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	$122.82	7.365%	$131.8657	$131.87	$131.85	$131.90
Purchase #2	$66.93	7.339%	$71.842	$71.84	$71.85	$71.80
Purchase #3	$48.66	8.332%	$52.7144	$52.71	$52.70	$52.70
Purchase #4	$140.98	6.475%	$150.1085	$150.11	$150.10	$150.10
Purchase #5	$37.71	4.254%	$39.3142	$39.31	$39.30	$39.30
Purchase #6	$142.32	4.162%	$148.2434	$148.24	$148.25	$148.20
Purchase #7	$193.34	10.483%	$213.6078	$213.61	$213.60	$213.60
7 purchase totals =	$752.76		$807.6960	$807.69	$807.65	$807.60