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	$129.71	7.601%	$139.5693	$139.57	$139.55	$139.60
Purchase #2	$140.50	13.229%	$159.0867	$159.09	$159.10	$159.10
Purchase #3	$240.96	6.617%	$256.9043	$256.90	$256.90	$256.90
Purchase #4	$73.94	11.222%	$82.2375	$82.24	$82.25	$82.20
Purchase #5	$138.31	11.290%	$153.9252	$153.93	$153.95	$153.90
Purchase #6	$82.73	11.198%	$91.9941	$91.99	$92.00	$92.00
Purchase #7	$122.51	4.716%	$128.2876	$128.29	$128.30	$128.30
7 purchase totals =	$928.66		$1,012.0047	$1,012.01	$1,012.05	$1,012.00