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	$175.38	10.443%	$193.6949	$193.69	$193.70	$193.70
Purchase #2	$217.27	12.226%	$243.8334	$243.83	$243.85	$243.80
Purchase #3	$119.43	11.562%	$133.2385	$133.24	$133.25	$133.20
Purchase #4	$30.93	9.310%	$33.8096	$33.81	$33.80	$33.80
Purchase #5	$92.26	11.106%	$102.5064	$102.51	$102.50	$102.50
Purchase #6	$137.59	11.131%	$152.9051	$152.91	$152.90	$152.90
Purchase #7	$82.62	8.719%	$89.8236	$89.82	$89.80	$89.80
7 purchase totals =	$855.48		$949.8115	$949.81	$949.80	$949.70