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	$22.44	11.131%	$24.9378	$24.94	$24.95	$24.90
Purchase #2	$44.42	13.420%	$50.3812	$50.38	$50.40	$50.40
Purchase #3	$244.69	12.686%	$275.7314	$275.73	$275.75	$275.70
Purchase #4	$11.99	11.712%	$13.3943	$13.39	$13.40	$13.40
Purchase #5	$89.75	12.439%	$100.914	$100.91	$100.90	$100.90
Purchase #6	$80.49	5.791%	$85.1512	$85.15	$85.15	$85.20
Purchase #7	$11.51	7.603%	$12.3851	$12.39	$12.40	$12.40
7 purchase totals =	$505.29		$562.8950	$562.89	$562.95	$562.90