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	$111.74	13.249%	$126.5444	$126.54	$126.55	$126.50
Purchase #2	$196.47	9.676%	$215.4804	$215.48	$215.50	$215.50
Purchase #3	$74.94	5.137%	$78.7897	$78.79	$78.80	$78.80
Purchase #4	$15.28	8.478%	$16.5754	$16.58	$16.60	$16.60
Purchase #5	$223.61	5.143%	$235.1103	$235.11	$235.10	$235.10
Purchase #6	$197.27	9.227%	$215.4721	$215.47	$215.45	$215.50
Purchase #7	$215.56	11.763%	$240.9163	$240.92	$240.90	$240.90
7 purchase totals =	$1,034.87		$1,128.8886	$1,128.89	$1,128.90	$1,128.90