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	$64.89	11.749%	$72.5139	$72.51	$72.50	$72.50
Purchase #2	$173.25	3.218%	$178.8252	$178.83	$178.85	$178.80
Purchase #3	$16.62	10.350%	$18.3402	$18.34	$18.35	$18.30
Purchase #4	$129.85	8.726%	$141.1807	$141.18	$141.20	$141.20
Purchase #5	$216.49	4.160%	$225.496	$225.50	$225.50	$225.50
Purchase #6	$35.78	10.596%	$39.5712	$39.57	$39.55	$39.60
Purchase #7	$55.59	8.740%	$60.4486	$60.45	$60.45	$60.40
7 purchase totals =	$692.47		$736.3758	$736.38	$736.40	$736.30