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	$153.89	7.438%	$165.3363	$165.34	$165.35	$165.30
Purchase #2	$56.81	8.490%	$61.6332	$61.63	$61.65	$61.60
Purchase #3	$128.77	11.108%	$143.0738	$143.07	$143.05	$143.10
Purchase #4	$83.36	8.549%	$90.4864	$90.49	$90.50	$90.50
Purchase #5	$236.71	12.804%	$267.0183	$267.02	$267.00	$267.00
Purchase #6	$187.31	7.811%	$201.9408	$201.94	$201.95	$201.90
Purchase #7	$87.89	13.221%	$99.5099	$99.51	$99.50	$99.50
7 purchase totals =	$934.74		$1,028.9987	$1,029.00	$1,029.00	$1,028.90