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	$222.78	8.864%	$242.5272	$242.53	$242.55	$242.50
Purchase #2	$152.70	8.401%	$165.5283	$165.53	$165.55	$165.50
Purchase #3	$198.74	13.781%	$226.1284	$226.13	$226.15	$226.10
Purchase #4	$202.59	13.344%	$229.6236	$229.62	$229.60	$229.60
Purchase #5	$113.81	11.685%	$127.1087	$127.11	$127.10	$127.10
Purchase #6	$97.72	13.745%	$111.1516	$111.15	$111.15	$111.20
Purchase #7	$61.57	10.585%	$68.0872	$68.09	$68.10	$68.10
7 purchase totals =	$1,049.91		$1,170.1550	$1,170.16	$1,170.20	$1,170.10