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	$246.46	3.823%	$255.8822	$255.88	$255.90	$255.90
Purchase #2	$190.71	13.383%	$216.2327	$216.23	$216.25	$216.20
Purchase #3	$139.44	8.192%	$150.8629	$150.86	$150.85	$150.90
Purchase #4	$155.41	3.711%	$161.1773	$161.18	$161.20	$161.20
Purchase #5	$68.99	5.190%	$72.5706	$72.57	$72.55	$72.60
Purchase #6	$232.59	7.579%	$250.218	$250.22	$250.20	$250.20
Purchase #7	$156.99	5.509%	$165.6386	$165.64	$165.65	$165.60
7 purchase totals =	$1,190.59		$1,272.5823	$1,272.58	$1,272.60	$1,272.60