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	$150.89	9.771%	$165.6335	$165.63	$165.65	$165.60
Purchase #2	$102.63	3.604%	$106.3288	$106.33	$106.35	$106.30
Purchase #3	$24.34	8.797%	$26.4812	$26.48	$26.50	$26.50
Purchase #4	$117.70	3.766%	$122.1326	$122.13	$122.15	$122.10
Purchase #5	$104.34	6.684%	$111.3141	$111.31	$111.30	$111.30
Purchase #6	$27.58	11.599%	$30.779	$30.78	$30.80	$30.80
Purchase #7	$179.34	9.768%	$196.8579	$196.86	$196.85	$196.90
7 purchase totals =	$706.82		$759.5271	$759.52	$759.60	$759.50