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	$189.45	11.549%	$211.3296	$211.33	$211.35	$211.30
Purchase #2	$29.42	8.288%	$31.8583	$31.86	$31.85	$31.90
Purchase #3	$158.68	13.103%	$179.4718	$179.47	$179.45	$179.50
Purchase #4	$144.43	10.733%	$159.9317	$159.93	$159.95	$159.90
Purchase #5	$180.85	6.142%	$191.9578	$191.96	$191.95	$192.00
Purchase #6	$227.61	11.541%	$253.8785	$253.88	$253.90	$253.90
Purchase #7	$125.38	8.509%	$136.0486	$136.05	$136.05	$136.00
7 purchase totals =	$1,055.82		$1,164.4763	$1,164.48	$1,164.50	$1,164.50