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	$161.78	7.319%	$173.6207	$173.62	$173.60	$173.60
Purchase #2	$79.45	12.444%	$89.3368	$89.34	$89.35	$89.30
Purchase #3	$28.63	5.217%	$30.1236	$30.12	$30.10	$30.10
Purchase #4	$59.65	3.129%	$61.5164	$61.52	$61.50	$61.50
Purchase #5	$90.98	3.667%	$94.3162	$94.32	$94.30	$94.30
Purchase #6	$130.58	8.338%	$141.4678	$141.47	$141.45	$141.50
Purchase #7	$159.54	3.271%	$164.7586	$164.76	$164.75	$164.80
7 purchase totals =	$710.61		$755.1401	$755.15	$755.05	$755.10