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	$102.40	9.245%	$111.8669	$111.87	$111.85	$111.90
Purchase #2	$6.65	11.390%	$7.4074	$7.41	$7.40	$7.40
Purchase #3	$182.31	5.586%	$192.4938	$192.49	$192.50	$192.50
Purchase #4	$92.53	3.703%	$95.9564	$95.96	$95.95	$96.00
Purchase #5	$185.43	3.265%	$191.4843	$191.48	$191.50	$191.50
Purchase #6	$51.45	12.840%	$58.0562	$58.06	$58.05	$58.10
Purchase #7	$81.46	13.663%	$92.5899	$92.59	$92.60	$92.60
7 purchase totals =	$702.23		$749.8549	$749.86	$749.85	$750.00