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	$41.25	11.171%	$45.858	$45.86	$45.85	$45.90
Purchase #2	$246.67	7.252%	$264.5585	$264.56	$264.55	$264.60
Purchase #3	$55.80	4.858%	$58.5108	$58.51	$58.50	$58.50
Purchase #4	$10.33	11.814%	$11.5504	$11.55	$11.55	$11.60
Purchase #5	$123.65	8.414%	$134.0539	$134.05	$134.05	$134.10
Purchase #6	$20.85	9.257%	$22.7801	$22.78	$22.80	$22.80
Purchase #7	$185.35	13.577%	$210.515	$210.52	$210.50	$210.50
7 purchase totals =	$683.90		$747.8267	$747.83	$747.80	$748.00