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	$83.30	13.861%	$94.8462	$94.85	$94.85	$94.80
Purchase #2	$83.32	7.670%	$89.7106	$89.71	$89.70	$89.70
Purchase #3	$248.51	3.138%	$256.3082	$256.31	$256.30	$256.30
Purchase #4	$80.88	13.847%	$92.0795	$92.08	$92.10	$92.10
Purchase #5	$195.39	5.697%	$206.5214	$206.52	$206.50	$206.50
Purchase #6	$133.61	4.198%	$139.2189	$139.22	$139.20	$139.20
Purchase #7	$67.81	12.315%	$76.1608	$76.16	$76.15	$76.20
7 purchase totals =	$892.82		$954.8456	$954.85	$954.80	$954.80