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	$141.37	12.105%	$158.4828	$158.48	$158.50	$158.50
Purchase #2	$92.63	8.249%	$100.271	$100.27	$100.25	$100.30
Purchase #3	$123.89	7.801%	$133.5547	$133.55	$133.55	$133.60
Purchase #4	$58.39	7.817%	$62.9543	$62.95	$62.95	$63.00
Purchase #5	$85.27	12.251%	$95.7164	$95.72	$95.70	$95.70
Purchase #6	$140.89	10.361%	$155.4876	$155.49	$155.50	$155.50
Purchase #7	$153.40	10.825%	$170.0056	$170.01	$170.00	$170.00
7 purchase totals =	$795.84		$876.4724	$876.47	$876.45	$876.60