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	$34.63	7.505%	$37.229	$37.23	$37.25	$37.20
Purchase #2	$85.26	6.617%	$90.9017	$90.90	$90.90	$90.90
Purchase #3	$236.74	12.263%	$265.7714	$265.77	$265.75	$265.80
Purchase #4	$234.74	10.536%	$259.4722	$259.47	$259.45	$259.50
Purchase #5	$84.49	8.828%	$91.9488	$91.95	$91.95	$91.90
Purchase #6	$240.60	5.666%	$254.2324	$254.23	$254.25	$254.20
Purchase #7	$247.83	10.586%	$274.0653	$274.07	$274.05	$274.10
7 purchase totals =	$1,164.29		$1,273.6208	$1,273.62	$1,273.60	$1,273.60