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	$11.44	7.284%	$12.2733	$12.27	$12.25	$12.30
Purchase #2	$40.55	11.397%	$45.1715	$45.17	$45.15	$45.20
Purchase #3	$56.54	7.682%	$60.8834	$60.88	$60.90	$60.90
Purchase #4	$161.47	5.871%	$170.9499	$170.95	$170.95	$170.90
Purchase #5	$153.69	5.872%	$162.7147	$162.71	$162.70	$162.70
Purchase #6	$245.53	5.427%	$258.8549	$258.85	$258.85	$258.90
Purchase #7	$229.64	10.377%	$253.4697	$253.47	$253.45	$253.50
7 purchase totals =	$898.86		$964.3174	$964.30	$964.25	$964.40