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	$233.49	9.698%	$256.1339	$256.13	$256.15	$256.10
Purchase #2	$191.69	11.179%	$213.119	$213.12	$213.10	$213.10
Purchase #3	$140.56	7.543%	$151.1624	$151.16	$151.15	$151.20
Purchase #4	$66.73	7.520%	$71.7481	$71.75	$71.75	$71.70
Purchase #5	$149.67	10.586%	$165.5141	$165.51	$165.50	$165.50
Purchase #6	$12.47	10.166%	$13.7377	$13.74	$13.75	$13.70
Purchase #7	$248.64	10.411%	$274.5259	$274.53	$274.55	$274.50
7 purchase totals =	$1,043.25		$1,145.9411	$1,145.94	$1,145.95	$1,145.80