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	$188.30	4.157%	$196.1276	$196.13	$196.15	$196.10
Purchase #2	$38.75	3.108%	$39.9544	$39.95	$39.95	$40.00
Purchase #3	$233.79	11.800%	$261.3772	$261.38	$261.40	$261.40
Purchase #4	$243.40	13.584%	$276.4635	$276.46	$276.45	$276.50
Purchase #5	$100.86	9.192%	$110.1311	$110.13	$110.15	$110.10
Purchase #6	$208.66	8.103%	$225.5677	$225.57	$225.55	$225.60
Purchase #7	$6.84	5.326%	$7.2043	$7.20	$7.20	$7.20
7 purchase totals =	$1,020.60		$1,116.8258	$1,116.82	$1,116.85	$1,116.90