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	$183.72	7.323%	$197.1738	$197.17	$197.15	$197.20
Purchase #2	$178.62	11.597%	$199.3346	$199.33	$199.35	$199.30
Purchase #3	$66.66	5.122%	$70.0743	$70.07	$70.05	$70.10
Purchase #4	$106.77	10.664%	$118.156	$118.16	$118.15	$118.20
Purchase #5	$124.72	13.445%	$141.4886	$141.49	$141.50	$141.50
Purchase #6	$92.61	8.437%	$100.4235	$100.42	$100.40	$100.40
Purchase #7	$169.32	4.426%	$176.8141	$176.81	$176.80	$176.80
7 purchase totals =	$922.42		$1,003.4649	$1,003.45	$1,003.40	$1,003.50