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	$228.48	13.772%	$259.9463	$259.95	$259.95	$259.90
Purchase #2	$176.51	9.845%	$193.8874	$193.89	$193.90	$193.90
Purchase #3	$158.96	4.111%	$165.4948	$165.49	$165.50	$165.50
Purchase #4	$149.25	9.178%	$162.9482	$162.95	$162.95	$162.90
Purchase #5	$247.25	12.369%	$277.8324	$277.83	$277.85	$277.80
Purchase #6	$180.49	8.724%	$196.2359	$196.24	$196.25	$196.20
Purchase #7	$82.48	11.437%	$91.9132	$91.91	$91.90	$91.90
7 purchase totals =	$1,223.42		$1,348.2582	$1,348.26	$1,348.30	$1,348.10