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	$152.64	9.248%	$166.7561	$166.76	$166.75	$166.80
Purchase #2	$80.55	9.573%	$88.2611	$88.26	$88.25	$88.30
Purchase #3	$238.33	7.785%	$256.884	$256.88	$256.90	$256.90
Purchase #4	$216.58	13.530%	$245.8833	$245.88	$245.90	$245.90
Purchase #5	$79.50	4.210%	$82.847	$82.85	$82.85	$82.80
Purchase #6	$223.94	12.111%	$251.0614	$251.06	$251.05	$251.10
Purchase #7	$243.31	11.576%	$271.4756	$271.48	$271.50	$271.50
7 purchase totals =	$1,234.85		$1,363.1685	$1,363.17	$1,363.20	$1,363.30