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	$207.42	7.151%	$222.2526	$222.25	$222.25	$222.30
Purchase #2	$125.66	12.592%	$141.4831	$141.48	$141.50	$141.50
Purchase #3	$108.26	11.761%	$120.9925	$120.99	$121.00	$121.00
Purchase #4	$180.87	11.379%	$201.4512	$201.45	$201.45	$201.50
Purchase #5	$168.77	11.712%	$188.5363	$188.54	$188.55	$188.50
Purchase #6	$83.27	3.733%	$86.3785	$86.38	$86.40	$86.40
Purchase #7	$67.89	4.742%	$71.1093	$71.11	$71.10	$71.10
7 purchase totals =	$942.14		$1,032.2035	$1,032.20	$1,032.25	$1,032.30