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	$250.44	13.259%	$283.6458	$283.65	$283.65	$283.60
Purchase #2	$60.57	10.328%	$66.8257	$66.83	$66.85	$66.80
Purchase #3	$144.90	7.527%	$155.8066	$155.81	$155.80	$155.80
Purchase #4	$37.39	7.318%	$40.1262	$40.13	$40.15	$40.10
Purchase #5	$50.72	13.220%	$57.4252	$57.43	$57.45	$57.40
Purchase #6	$142.88	11.865%	$159.8327	$159.83	$159.85	$159.80
Purchase #7	$220.59	11.756%	$246.5226	$246.52	$246.50	$246.50
7 purchase totals =	$907.49		$1,010.1848	$1,010.20	$1,010.25	$1,010.00