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	$67.51	6.555%	$71.9353	$71.94	$71.95	$71.90
Purchase #2	$55.54	7.370%	$59.6333	$59.63	$59.65	$59.60
Purchase #3	$143.53	6.409%	$152.7288	$152.73	$152.75	$152.70
Purchase #4	$77.31	12.150%	$86.7032	$86.70	$86.70	$86.70
Purchase #5	$211.65	13.700%	$240.6461	$240.65	$240.65	$240.60
Purchase #6	$165.75	11.594%	$184.9671	$184.97	$184.95	$185.00
Purchase #7	$139.95	13.188%	$158.4066	$158.41	$158.40	$158.40
7 purchase totals =	$861.24		$955.0204	$955.03	$955.05	$954.90