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	$169.91	11.331%	$189.1625	$189.16	$189.15	$189.20
Purchase #2	$173.29	5.449%	$182.7326	$182.73	$182.75	$182.70
Purchase #3	$177.65	11.167%	$197.4882	$197.49	$197.50	$197.50
Purchase #4	$29.92	13.167%	$33.8596	$33.86	$33.85	$33.90
Purchase #5	$54.71	9.467%	$59.8894	$59.89	$59.90	$59.90
Purchase #6	$201.30	4.237%	$209.8291	$209.83	$209.85	$209.80
Purchase #7	$248.53	11.845%	$277.9684	$277.97	$277.95	$278.00
7 purchase totals =	$1,055.31		$1,150.9298	$1,150.93	$1,150.95	$1,151.00