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	$113.55	10.223%	$125.1582	$125.16	$125.15	$125.20
Purchase #2	$57.45	6.733%	$61.3181	$61.32	$61.30	$61.30
Purchase #3	$115.40	10.603%	$127.6359	$127.64	$127.65	$127.60
Purchase #4	$20.28	4.365%	$21.1652	$21.17	$21.15	$21.20
Purchase #5	$39.87	10.429%	$44.028	$44.03	$44.05	$44.00
Purchase #6	$148.81	13.315%	$168.6241	$168.62	$168.60	$168.60
Purchase #7	$132.74	3.805%	$137.7908	$137.79	$137.80	$137.80
7 purchase totals =	$628.10		$685.7203	$685.73	$685.70	$685.70