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	$107.67	9.178%	$117.552	$117.55	$117.55	$117.60
Purchase #2	$77.58	8.136%	$83.8919	$83.89	$83.90	$83.90
Purchase #3	$72.80	7.620%	$78.3474	$78.35	$78.35	$78.30
Purchase #4	$84.72	4.539%	$88.5654	$88.57	$88.55	$88.60
Purchase #5	$132.74	10.348%	$146.4759	$146.48	$146.50	$146.50
Purchase #6	$233.88	3.114%	$241.163	$241.16	$241.15	$241.20
Purchase #7	$113.78	9.134%	$124.1727	$124.17	$124.15	$124.20
7 purchase totals =	$823.17		$880.1683	$880.17	$880.15	$880.30