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	$192.32	3.319%	$198.7031	$198.70	$198.70	$198.70
Purchase #2	$158.37	7.699%	$170.5629	$170.56	$170.55	$170.60
Purchase #3	$137.65	7.527%	$148.0109	$148.01	$148.00	$148.00
Purchase #4	$61.56	8.125%	$66.5618	$66.56	$66.55	$66.60
Purchase #5	$132.61	9.570%	$145.3008	$145.30	$145.30	$145.30
Purchase #6	$150.29	8.143%	$162.5281	$162.53	$162.55	$162.50
Purchase #7	$63.56	13.124%	$71.9016	$71.90	$71.90	$71.90
7 purchase totals =	$896.36		$963.5692	$963.56	$963.55	$963.60