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	$203.87	8.505%	$221.2091	$221.21	$221.20	$221.20
Purchase #2	$112.41	3.530%	$116.3781	$116.38	$116.40	$116.40
Purchase #3	$220.37	7.818%	$237.5985	$237.60	$237.60	$237.60
Purchase #4	$57.58	7.478%	$61.8858	$61.89	$61.90	$61.90
Purchase #5	$94.44	5.431%	$99.569	$99.57	$99.55	$99.60
Purchase #6	$216.91	12.685%	$244.425	$244.43	$244.45	$244.40
Purchase #7	$241.39	13.573%	$274.1539	$274.15	$274.15	$274.20
7 purchase totals =	$1,146.97		$1,255.2194	$1,255.23	$1,255.25	$1,255.30