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	$85.47	8.669%	$92.8794	$92.88	$92.90	$92.90
Purchase #2	$191.89	13.592%	$217.9717	$217.97	$217.95	$218.00
Purchase #3	$99.34	6.376%	$105.6739	$105.67	$105.65	$105.70
Purchase #4	$172.34	11.548%	$192.2418	$192.24	$192.25	$192.20
Purchase #5	$185.47	13.803%	$211.0704	$211.07	$211.05	$211.10
Purchase #6	$221.50	10.547%	$244.8616	$244.86	$244.85	$244.90
Purchase #7	$18.64	13.857%	$21.2229	$21.22	$21.20	$21.20
7 purchase totals =	$974.65		$1,085.9217	$1,085.91	$1,085.85	$1,086.00