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	$161.92	6.140%	$171.8619	$171.86	$171.85	$171.90
Purchase #2	$162.55	9.120%	$177.3746	$177.37	$177.35	$177.40
Purchase #3	$53.47	3.767%	$55.4842	$55.48	$55.50	$55.50
Purchase #4	$34.31	8.453%	$37.2102	$37.21	$37.20	$37.20
Purchase #5	$100.75	9.196%	$110.015	$110.02	$110.00	$110.00
Purchase #6	$53.81	13.428%	$61.0356	$61.04	$61.05	$61.00
Purchase #7	$226.51	12.832%	$255.5758	$255.58	$255.60	$255.60
7 purchase totals =	$793.32		$868.5573	$868.56	$868.55	$868.60