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	$137.87	11.469%	$153.6823	$153.68	$153.70	$153.70
Purchase #2	$94.75	5.220%	$99.696	$99.70	$99.70	$99.70
Purchase #3	$90.49	4.666%	$94.7123	$94.71	$94.70	$94.70
Purchase #4	$56.82	8.313%	$61.5434	$61.54	$61.55	$61.50
Purchase #5	$59.27	13.597%	$67.3289	$67.33	$67.35	$67.30
Purchase #6	$211.25	9.733%	$231.811	$231.81	$231.80	$231.80
Purchase #7	$47.97	8.118%	$51.8642	$51.86	$51.85	$51.90
7 purchase totals =	$698.42		$760.6381	$760.63	$760.65	$760.60