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	$184.93	6.375%	$196.7193	$196.72	$196.70	$196.70
Purchase #2	$105.33	3.640%	$109.164	$109.16	$109.15	$109.20
Purchase #3	$126.39	8.290%	$136.8677	$136.87	$136.85	$136.90
Purchase #4	$143.69	10.602%	$158.924	$158.92	$158.90	$158.90
Purchase #5	$10.97	11.491%	$12.2306	$12.23	$12.25	$12.20
Purchase #6	$24.90	5.620%	$26.2994	$26.30	$26.30	$26.30
Purchase #7	$94.80	3.735%	$98.3408	$98.34	$98.35	$98.30
7 purchase totals =	$691.01		$738.5458	$738.54	$738.50	$738.50