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	$233.72	6.663%	$249.2928	$249.29	$249.30	$249.30
Purchase #2	$126.29	11.750%	$141.1291	$141.13	$141.15	$141.10
Purchase #3	$241.50	5.504%	$254.7922	$254.79	$254.80	$254.80
Purchase #4	$119.91	5.303%	$126.2688	$126.27	$126.25	$126.30
Purchase #5	$151.67	11.437%	$169.0165	$169.02	$169.00	$169.00
Purchase #6	$9.30	11.462%	$10.366	$10.37	$10.35	$10.40
Purchase #7	$56.94	4.705%	$59.619	$59.62	$59.60	$59.60
7 purchase totals =	$939.33		$1,010.4844	$1,010.49	$1,010.45	$1,010.50