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	$32.28	7.172%	$34.5951	$34.60	$34.60	$34.60
Purchase #2	$242.92	4.749%	$254.4563	$254.46	$254.45	$254.50
Purchase #3	$78.61	6.332%	$83.5876	$83.59	$83.60	$83.60
Purchase #4	$191.98	12.660%	$216.2847	$216.28	$216.30	$216.30
Purchase #5	$37.95	3.154%	$39.1469	$39.15	$39.15	$39.10
Purchase #6	$184.96	13.614%	$210.1405	$210.14	$210.15	$210.10
Purchase #7	$238.55	3.738%	$247.467	$247.47	$247.45	$247.50
7 purchase totals =	$1,007.25		$1,085.6781	$1,085.69	$1,085.70	$1,085.70