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	$55.54	4.146%	$57.8427	$57.84	$57.85	$57.80
Purchase #2	$39.68	7.603%	$42.6969	$42.70	$42.70	$42.70
Purchase #3	$50.41	9.176%	$55.0356	$55.04	$55.05	$55.00
Purchase #4	$150.95	3.418%	$156.1095	$156.11	$156.10	$156.10
Purchase #5	$159.77	3.808%	$165.854	$165.85	$165.85	$165.90
Purchase #6	$156.35	4.468%	$163.3357	$163.34	$163.35	$163.30
Purchase #7	$72.51	8.561%	$78.7176	$78.72	$78.70	$78.70
7 purchase totals =	$685.21		$719.5920	$719.60	$719.60	$719.50