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	$95.37	6.224%	$101.3058	$101.31	$101.30	$101.30
Purchase #2	$56.27	10.105%	$61.9561	$61.96	$61.95	$62.00
Purchase #3	$87.61	3.317%	$90.516	$90.52	$90.50	$90.50
Purchase #4	$53.45	12.262%	$60.004	$60.00	$60.00	$60.00
Purchase #5	$129.42	7.178%	$138.7098	$138.71	$138.70	$138.70
Purchase #6	$51.27	10.171%	$56.4847	$56.48	$56.50	$56.50
Purchase #7	$29.34	3.700%	$30.4256	$30.43	$30.45	$30.40
7 purchase totals =	$502.73		$539.4020	$539.41	$539.40	$539.40