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	$130.50	7.785%	$140.6594	$140.66	$140.65	$140.70
Purchase #2	$83.39	9.655%	$91.4413	$91.44	$91.45	$91.40
Purchase #3	$35.81	4.484%	$37.4157	$37.42	$37.40	$37.40
Purchase #4	$62.39	13.429%	$70.7684	$70.77	$70.75	$70.80
Purchase #5	$214.38	7.862%	$231.2346	$231.23	$231.25	$231.20
Purchase #6	$169.87	3.521%	$175.8511	$175.85	$175.85	$175.90
Purchase #7	$77.66	7.552%	$83.5249	$83.52	$83.50	$83.50
7 purchase totals =	$774.00		$830.8954	$830.89	$830.85	$830.90