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	$209.67	10.380%	$231.4337	$231.43	$231.45	$231.40
Purchase #2	$18.67	11.678%	$20.8503	$20.85	$20.85	$20.90
Purchase #3	$27.69	5.284%	$29.1531	$29.15	$29.15	$29.20
Purchase #4	$234.49	8.380%	$254.1403	$254.14	$254.15	$254.10
Purchase #5	$167.66	8.532%	$181.9648	$181.96	$181.95	$182.00
Purchase #6	$249.86	13.400%	$283.3412	$283.34	$283.35	$283.30
Purchase #7	$134.83	12.443%	$151.6069	$151.61	$151.60	$151.60
7 purchase totals =	$1,042.87		$1,152.4903	$1,152.48	$1,152.50	$1,152.50