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	$148.56	4.589%	$155.3774	$155.38	$155.40	$155.40
Purchase #2	$71.93	3.241%	$74.2613	$74.26	$74.25	$74.30
Purchase #3	$220.32	4.284%	$229.7585	$229.76	$229.75	$229.80
Purchase #4	$58.29	13.294%	$66.0391	$66.04	$66.05	$66.00
Purchase #5	$36.72	9.778%	$40.3105	$40.31	$40.30	$40.30
Purchase #6	$10.77	6.277%	$11.446	$11.45	$11.45	$11.40
Purchase #7	$90.80	8.254%	$98.2946	$98.29	$98.30	$98.30
7 purchase totals =	$637.39		$675.4874	$675.49	$675.50	$675.50