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	$72.71	13.596%	$82.5957	$82.60	$82.60	$82.60
Purchase #2	$29.76	9.292%	$32.5253	$32.53	$32.55	$32.50
Purchase #3	$87.95	12.841%	$99.2437	$99.24	$99.25	$99.20
Purchase #4	$152.71	9.178%	$166.7257	$166.73	$166.75	$166.70
Purchase #5	$104.51	13.351%	$118.4631	$118.46	$118.45	$118.50
Purchase #6	$22.80	12.312%	$25.6071	$25.61	$25.60	$25.60
Purchase #7	$37.49	12.433%	$42.1511	$42.15	$42.15	$42.20
7 purchase totals =	$507.93		$567.3117	$567.32	$567.35	$567.30