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	$132.78	10.531%	$146.7631	$146.76	$146.75	$146.80
Purchase #2	$160.75	6.695%	$171.5122	$171.51	$171.50	$171.50
Purchase #3	$46.75	5.826%	$49.4737	$49.47	$49.45	$49.50
Purchase #4	$50.37	5.771%	$53.2769	$53.28	$53.30	$53.30
Purchase #5	$238.46	10.473%	$263.4339	$263.43	$263.45	$263.40
Purchase #6	$192.90	11.390%	$214.8713	$214.87	$214.85	$214.90
Purchase #7	$99.53	11.462%	$110.9381	$110.94	$110.95	$110.90
7 purchase totals =	$921.54		$1,010.2692	$1,010.26	$1,010.25	$1,010.30