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	$125.78	3.861%	$130.6364	$130.64	$130.65	$130.60
Purchase #2	$129.98	5.832%	$137.5604	$137.56	$137.55	$137.60
Purchase #3	$121.39	13.311%	$137.5482	$137.55	$137.55	$137.50
Purchase #4	$66.76	13.243%	$75.601	$75.60	$75.60	$75.60
Purchase #5	$64.56	10.236%	$71.1684	$71.17	$71.15	$71.20
Purchase #6	$16.45	12.204%	$18.4576	$18.46	$18.45	$18.50
Purchase #7	$184.59	3.817%	$191.6358	$191.64	$191.65	$191.60
7 purchase totals =	$709.51		$762.6078	$762.62	$762.60	$762.60