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	$125.27	4.822%	$131.3105	$131.31	$131.30	$131.30
Purchase #2	$78.66	5.778%	$83.205	$83.21	$83.20	$83.20
Purchase #3	$22.70	10.662%	$25.1203	$25.12	$25.10	$25.10
Purchase #4	$80.72	9.503%	$88.3908	$88.39	$88.40	$88.40
Purchase #5	$150.83	11.828%	$168.6702	$168.67	$168.65	$168.70
Purchase #6	$225.45	10.671%	$249.5078	$249.51	$249.50	$249.50
Purchase #7	$6.51	13.800%	$7.4084	$7.41	$7.40	$7.40
7 purchase totals =	$690.14		$753.6130	$753.62	$753.55	$753.60