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	$156.38	5.459%	$164.9168	$164.92	$164.90	$164.90
Purchase #2	$93.32	13.774%	$106.1739	$106.17	$106.15	$106.20
Purchase #3	$137.62	6.467%	$146.5199	$146.52	$146.50	$146.50
Purchase #4	$143.78	10.500%	$158.8769	$158.88	$158.90	$158.90
Purchase #5	$51.40	13.823%	$58.505	$58.51	$58.50	$58.50
Purchase #6	$131.42	4.742%	$137.6519	$137.65	$137.65	$137.70
Purchase #7	$138.89	3.449%	$143.6803	$143.68	$143.70	$143.70
7 purchase totals =	$852.81		$916.3247	$916.33	$916.30	$916.40