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	$119.69	8.729%	$130.1377	$130.14	$130.15	$130.10
Purchase #2	$137.68	4.539%	$143.9293	$143.93	$143.95	$143.90
Purchase #3	$83.52	11.182%	$92.8592	$92.86	$92.85	$92.90
Purchase #4	$140.93	3.822%	$146.3163	$146.32	$146.30	$146.30
Purchase #5	$71.86	13.847%	$81.8105	$81.81	$81.80	$81.80
Purchase #6	$110.60	8.848%	$120.3859	$120.39	$120.40	$120.40
Purchase #7	$77.48	10.718%	$85.7843	$85.78	$85.80	$85.80
7 purchase totals =	$741.76		$801.2232	$801.23	$801.25	$801.20