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	$82.63	6.691%	$88.1588	$88.16	$88.15	$88.20
Purchase #2	$104.43	8.664%	$113.4778	$113.48	$113.50	$113.50
Purchase #3	$151.27	3.738%	$156.9245	$156.92	$156.90	$156.90
Purchase #4	$23.76	13.718%	$27.0194	$27.02	$27.00	$27.00
Purchase #5	$17.58	3.138%	$18.1317	$18.13	$18.15	$18.10
Purchase #6	$40.72	10.688%	$45.0722	$45.07	$45.05	$45.10
Purchase #7	$50.49	11.366%	$56.2287	$56.23	$56.25	$56.20
7 purchase totals =	$470.88		$505.0131	$505.01	$505.00	$505.00