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	$225.41	13.370%	$255.5473	$255.55	$255.55	$255.50
Purchase #2	$122.53	6.610%	$130.6292	$130.63	$130.65	$130.60
Purchase #3	$95.81	8.365%	$103.8245	$103.82	$103.80	$103.80
Purchase #4	$52.91	11.791%	$59.1486	$59.15	$59.15	$59.10
Purchase #5	$156.54	6.481%	$166.6854	$166.69	$166.70	$166.70
Purchase #6	$146.79	3.614%	$152.095	$152.10	$152.10	$152.10
Purchase #7	$241.40	8.627%	$262.2256	$262.23	$262.25	$262.20
7 purchase totals =	$1,041.39		$1,130.1556	$1,130.17	$1,130.20	$1,130.00