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	$50.95	13.370%	$57.762	$57.76	$57.75	$57.80
Purchase #2	$24.43	10.137%	$26.9065	$26.91	$26.90	$26.90
Purchase #3	$151.51	9.340%	$165.661	$165.66	$165.65	$165.70
Purchase #4	$164.48	5.578%	$173.6547	$173.65	$173.65	$173.70
Purchase #5	$182.77	7.414%	$196.3206	$196.32	$196.30	$196.30
Purchase #6	$159.69	4.594%	$167.0262	$167.03	$167.05	$167.00
Purchase #7	$70.84	11.417%	$78.9278	$78.93	$78.95	$78.90
7 purchase totals =	$804.67		$866.2588	$866.26	$866.25	$866.30