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	$139.75	8.657%	$151.8482	$151.85	$151.85	$151.80
Purchase #2	$156.42	5.702%	$165.3391	$165.34	$165.35	$165.30
Purchase #3	$7.85	4.204%	$8.18	$8.18	$8.20	$8.20
Purchase #4	$129.62	6.174%	$137.6227	$137.62	$137.60	$137.60
Purchase #5	$56.51	4.419%	$59.0072	$59.01	$59.00	$59.00
Purchase #6	$225.91	7.523%	$242.9052	$242.91	$242.90	$242.90
Purchase #7	$171.83	11.513%	$191.6128	$191.61	$191.60	$191.60
7 purchase totals =	$887.89		$956.5152	$956.52	$956.50	$956.40