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	$221.59	4.206%	$230.9101	$230.91	$230.90	$230.90
Purchase #2	$100.70	7.557%	$108.3099	$108.31	$108.30	$108.30
Purchase #3	$164.31	4.769%	$172.1459	$172.15	$172.15	$172.10
Purchase #4	$37.93	5.635%	$40.0674	$40.07	$40.05	$40.10
Purchase #5	$42.80	5.862%	$45.3089	$45.31	$45.30	$45.30
Purchase #6	$110.90	6.769%	$118.4068	$118.41	$118.40	$118.40
Purchase #7	$37.26	12.333%	$41.8553	$41.86	$41.85	$41.90
7 purchase totals =	$715.49		$757.0043	$757.02	$756.95	$757.00