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	$219.30	7.358%	$235.4361	$235.44	$235.45	$235.40
Purchase #2	$90.98	5.757%	$96.2177	$96.22	$96.20	$96.20
Purchase #3	$248.43	5.468%	$262.0142	$262.01	$262.00	$262.00
Purchase #4	$152.89	4.188%	$159.293	$159.29	$159.30	$159.30
Purchase #5	$40.75	12.432%	$45.816	$45.82	$45.80	$45.80
Purchase #6	$196.31	12.755%	$221.3493	$221.35	$221.35	$221.30
Purchase #7	$46.51	8.301%	$50.3708	$50.37	$50.35	$50.40
7 purchase totals =	$995.17		$1,070.4971	$1,070.50	$1,070.45	$1,070.40