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	$90.93	11.275%	$101.1824	$101.18	$101.20	$101.20
Purchase #2	$132.84	11.759%	$148.4607	$148.46	$148.45	$148.50
Purchase #3	$77.91	5.283%	$82.026	$82.03	$82.05	$82.00
Purchase #4	$151.51	4.359%	$158.1143	$158.11	$158.10	$158.10
Purchase #5	$148.45	6.618%	$158.2744	$158.27	$158.25	$158.30
Purchase #6	$55.33	12.813%	$62.4194	$62.42	$62.40	$62.40
Purchase #7	$157.30	8.184%	$170.1734	$170.17	$170.15	$170.20
7 purchase totals =	$814.27		$880.6506	$880.64	$880.60	$880.70