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	$67.33	6.234%	$71.5274	$71.53	$71.55	$71.50
Purchase #2	$111.55	13.143%	$126.211	$126.21	$126.20	$126.20
Purchase #3	$229.55	10.281%	$253.15	$253.15	$253.15	$253.20
Purchase #4	$56.88	12.694%	$64.1003	$64.10	$64.10	$64.10
Purchase #5	$210.46	7.327%	$225.8804	$225.88	$225.90	$225.90
Purchase #6	$196.45	10.722%	$217.5134	$217.51	$217.50	$217.50
Purchase #7	$138.69	11.772%	$155.0166	$155.02	$155.00	$155.00
7 purchase totals =	$1,010.91		$1,113.3991	$1,113.40	$1,113.40	$1,113.40