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	$55.96	7.671%	$60.2527	$60.25	$60.25	$60.30
Purchase #2	$34.77	4.163%	$36.2175	$36.22	$36.20	$36.20
Purchase #3	$198.72	12.295%	$223.1526	$223.15	$223.15	$223.20
Purchase #4	$127.58	7.679%	$137.3769	$137.38	$137.40	$137.40
Purchase #5	$137.62	6.687%	$146.8226	$146.82	$146.80	$146.80
Purchase #6	$248.43	4.512%	$259.6392	$259.64	$259.65	$259.60
Purchase #7	$79.54	7.345%	$85.3822	$85.38	$85.40	$85.40
7 purchase totals =	$882.62		$948.8437	$948.84	$948.85	$948.90