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	$216.67	7.614%	$233.1673	$233.17	$233.15	$233.20
Purchase #2	$141.38	5.362%	$148.9608	$148.96	$148.95	$149.00
Purchase #3	$153.57	3.370%	$158.7453	$158.75	$158.75	$158.70
Purchase #4	$57.93	5.871%	$61.3311	$61.33	$61.35	$61.30
Purchase #5	$242.51	3.381%	$250.7093	$250.71	$250.70	$250.70
Purchase #6	$66.94	7.742%	$72.1225	$72.12	$72.10	$72.10
Purchase #7	$138.60	6.479%	$147.5799	$147.58	$147.60	$147.60
7 purchase totals =	$1,017.60		$1,072.6162	$1,072.62	$1,072.60	$1,072.60