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	$206.37	5.212%	$217.126	$217.13	$217.15	$217.10
Purchase #2	$83.34	7.551%	$89.633	$89.63	$89.65	$89.60
Purchase #3	$128.74	11.837%	$143.979	$143.98	$144.00	$144.00
Purchase #4	$194.32	13.377%	$220.3142	$220.31	$220.30	$220.30
Purchase #5	$35.74	10.470%	$39.482	$39.48	$39.50	$39.50
Purchase #6	$167.28	10.344%	$184.5834	$184.58	$184.60	$184.60
Purchase #7	$196.89	10.550%	$217.6619	$217.66	$217.65	$217.70
7 purchase totals =	$1,012.68		$1,112.7795	$1,112.77	$1,112.85	$1,112.80