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	$72.50	5.429%	$76.436	$76.44	$76.45	$76.40
Purchase #2	$92.39	7.560%	$99.3747	$99.37	$99.35	$99.40
Purchase #3	$74.79	12.485%	$84.1275	$84.13	$84.15	$84.10
Purchase #4	$55.45	10.245%	$61.1309	$61.13	$61.15	$61.10
Purchase #5	$9.89	3.275%	$10.2139	$10.21	$10.20	$10.20
Purchase #6	$98.28	13.371%	$111.421	$111.42	$111.40	$111.40
Purchase #7	$195.27	5.583%	$206.1719	$206.17	$206.15	$206.20
7 purchase totals =	$598.57		$648.8759	$648.87	$648.85	$648.80