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	$229.81	3.822%	$238.5933	$238.59	$238.60	$238.60
Purchase #2	$58.72	5.838%	$62.1481	$62.15	$62.15	$62.10
Purchase #3	$118.57	7.693%	$127.6916	$127.69	$127.70	$127.70
Purchase #4	$208.98	3.395%	$216.0749	$216.07	$216.05	$216.10
Purchase #5	$228.63	7.114%	$244.8947	$244.89	$244.90	$244.90
Purchase #6	$55.98	5.826%	$59.2414	$59.24	$59.25	$59.20
Purchase #7	$77.34	8.699%	$84.0678	$84.07	$84.05	$84.10
7 purchase totals =	$978.03		$1,032.7118	$1,032.70	$1,032.70	$1,032.70