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	$15.88	11.223%	$17.6622	$17.66	$17.65	$17.70
Purchase #2	$188.51	11.179%	$209.5835	$209.58	$209.60	$209.60
Purchase #3	$184.66	6.429%	$196.5318	$196.53	$196.55	$196.50
Purchase #4	$202.94	6.186%	$215.4939	$215.49	$215.50	$215.50
Purchase #5	$209.74	7.516%	$225.5041	$225.50	$225.50	$225.50
Purchase #6	$24.67	10.267%	$27.2029	$27.20	$27.20	$27.20
Purchase #7	$121.83	9.150%	$132.9774	$132.98	$133.00	$133.00
7 purchase totals =	$948.23		$1,024.9558	$1,024.94	$1,025.00	$1,025.00