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	$212.48	8.359%	$230.2412	$230.24	$230.25	$230.20
Purchase #2	$81.56	5.644%	$86.1632	$86.16	$86.15	$86.20
Purchase #3	$49.68	13.732%	$56.5021	$56.50	$56.50	$56.50
Purchase #4	$56.28	5.484%	$59.3664	$59.37	$59.35	$59.40
Purchase #5	$46.51	7.664%	$50.0745	$50.07	$50.05	$50.10
Purchase #6	$209.43	5.652%	$221.267	$221.27	$221.25	$221.30
Purchase #7	$51.96	13.769%	$59.1144	$59.11	$59.10	$59.10
7 purchase totals =	$707.90		$762.7288	$762.72	$762.65	$762.80