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	$95.51	4.428%	$99.7392	$99.74	$99.75	$99.70
Purchase #2	$176.60	11.307%	$196.5682	$196.57	$196.55	$196.60
Purchase #3	$143.38	6.447%	$152.6237	$152.62	$152.60	$152.60
Purchase #4	$57.49	6.316%	$61.1211	$61.12	$61.10	$61.10
Purchase #5	$171.75	7.605%	$184.8116	$184.81	$184.80	$184.80
Purchase #6	$149.30	7.696%	$160.7901	$160.79	$160.80	$160.80
Purchase #7	$208.41	8.149%	$225.3933	$225.39	$225.40	$225.40
7 purchase totals =	$1,002.44		$1,081.0472	$1,081.04	$1,081.00	$1,081.00