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	$30.90	8.185%	$33.4292	$33.43	$33.45	$33.40
Purchase #2	$232.59	12.694%	$262.115	$262.12	$262.10	$262.10
Purchase #3	$151.89	5.668%	$160.4991	$160.50	$160.50	$160.50
Purchase #4	$47.51	3.617%	$49.2284	$49.23	$49.25	$49.20
Purchase #5	$62.27	6.684%	$66.4321	$66.43	$66.45	$66.40
Purchase #6	$130.74	9.726%	$143.4558	$143.46	$143.45	$143.50
Purchase #7	$41.56	11.186%	$46.2089	$46.21	$46.20	$46.20
7 purchase totals =	$697.46		$761.3685	$761.38	$761.40	$761.30