Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$99.38	9.626%	$108.9463	$108.95	$108.95	$108.90
Purchase #2	$250.43	13.738%	$284.8341	$284.83	$284.85	$284.80
Purchase #3	$80.87	9.536%	$88.5818	$88.58	$88.60	$88.60
Purchase #4	$242.86	5.535%	$256.3023	$256.30	$256.30	$256.30
Purchase #5	$237.38	11.375%	$264.382	$264.38	$264.40	$264.40
Purchase #6	$172.59	11.102%	$191.7509	$191.75	$191.75	$191.80
Purchase #7	$174.79	9.152%	$190.7868	$190.79	$190.80	$190.80
7 purchase totals =	$1,258.30		$1,385.5842	$1,385.58	$1,385.65	$1,385.60