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	$200.47	11.199%	$222.9206	$222.92	$222.90	$222.90
Purchase #2	$44.39	13.414%	$50.3445	$50.34	$50.35	$50.30
Purchase #3	$231.54	5.541%	$244.3696	$244.37	$244.35	$244.40
Purchase #4	$35.25	7.517%	$37.8997	$37.90	$37.90	$37.90
Purchase #5	$16.88	6.670%	$18.0059	$18.01	$18.00	$18.00
Purchase #6	$230.39	8.757%	$250.5653	$250.57	$250.55	$250.60
Purchase #7	$145.45	5.338%	$153.2141	$153.21	$153.20	$153.20
7 purchase totals =	$904.37		$977.3197	$977.32	$977.25	$977.30