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	$140.99	9.142%	$153.8793	$153.88	$153.90	$153.90
Purchase #2	$249.44	10.463%	$275.5389	$275.54	$275.55	$275.50
Purchase #3	$236.88	7.575%	$254.8237	$254.82	$254.80	$254.80
Purchase #4	$112.91	8.665%	$122.6937	$122.69	$122.70	$122.70
Purchase #5	$158.54	8.775%	$172.4519	$172.45	$172.45	$172.50
Purchase #6	$40.72	7.210%	$43.6559	$43.66	$43.65	$43.70
Purchase #7	$64.42	11.545%	$71.8573	$71.86	$71.85	$71.90
7 purchase totals =	$1,003.90		$1,094.9007	$1,094.90	$1,094.90	$1,095.00