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	$193.86	12.853%	$218.7768	$218.78	$218.80	$218.80
Purchase #2	$49.30	7.806%	$53.1484	$53.15	$53.15	$53.10
Purchase #3	$116.68	3.612%	$120.8945	$120.89	$120.90	$120.90
Purchase #4	$84.87	9.733%	$93.1304	$93.13	$93.15	$93.10
Purchase #5	$30.74	4.168%	$32.0212	$32.02	$32.00	$32.00
Purchase #6	$59.55	3.150%	$61.4258	$61.43	$61.45	$61.40
Purchase #7	$93.36	13.179%	$105.6639	$105.66	$105.65	$105.70
7 purchase totals =	$628.36		$685.0610	$685.06	$685.10	$685.00