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	$35.42	7.102%	$37.9355	$37.94	$37.95	$37.90
Purchase #2	$250.84	6.667%	$267.5635	$267.56	$267.55	$267.60
Purchase #3	$142.83	9.519%	$156.426	$156.43	$156.45	$156.40
Purchase #4	$126.55	6.502%	$134.7783	$134.78	$134.80	$134.80
Purchase #5	$173.80	4.823%	$182.1824	$182.18	$182.20	$182.20
Purchase #6	$199.72	11.634%	$222.9554	$222.96	$222.95	$223.00
Purchase #7	$143.94	5.434%	$151.7617	$151.76	$151.75	$151.80
7 purchase totals =	$1,073.10		$1,153.6028	$1,153.61	$1,153.65	$1,153.70