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	$87.68	3.600%	$90.8365	$90.84	$90.85	$90.80
Purchase #2	$214.93	13.136%	$243.1632	$243.16	$243.15	$243.20
Purchase #3	$152.76	11.251%	$169.947	$169.95	$169.95	$169.90
Purchase #4	$111.50	11.360%	$124.1664	$124.17	$124.15	$124.20
Purchase #5	$148.55	11.837%	$166.1339	$166.13	$166.15	$166.10
Purchase #6	$209.71	13.817%	$238.6856	$238.69	$238.70	$238.70
Purchase #7	$15.64	6.460%	$16.6503	$16.65	$16.65	$16.70
7 purchase totals =	$940.77		$1,049.5829	$1,049.59	$1,049.60	$1,049.60