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	$230.88	6.192%	$245.1761	$245.18	$245.20	$245.20
Purchase #2	$70.25	11.388%	$78.2501	$78.25	$78.25	$78.30
Purchase #3	$43.91	3.698%	$45.5338	$45.53	$45.55	$45.50
Purchase #4	$63.81	4.427%	$66.6349	$66.63	$66.65	$66.60
Purchase #5	$222.52	6.578%	$237.1574	$237.16	$237.15	$237.20
Purchase #6	$235.54	8.619%	$255.8412	$255.84	$255.85	$255.80
Purchase #7	$193.47	5.298%	$203.72	$203.72	$203.70	$203.70
7 purchase totals =	$1,060.38		$1,132.3135	$1,132.31	$1,132.35	$1,132.30