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	$98.25	11.756%	$109.8003	$109.80	$109.80	$109.80
Purchase #2	$171.33	11.602%	$191.2077	$191.21	$191.20	$191.20
Purchase #3	$214.69	11.858%	$240.1479	$240.15	$240.15	$240.10
Purchase #4	$189.34	10.667%	$209.5369	$209.54	$209.55	$209.50
Purchase #5	$239.83	6.772%	$256.0713	$256.07	$256.05	$256.10
Purchase #6	$112.36	12.165%	$126.0286	$126.03	$126.05	$126.00
Purchase #7	$17.40	5.733%	$18.3975	$18.40	$18.40	$18.40
7 purchase totals =	$1,043.20		$1,151.1902	$1,151.20	$1,151.20	$1,151.10