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	$85.96	4.435%	$89.7723	$89.77	$89.75	$89.80
Purchase #2	$228.51	13.612%	$259.6148	$259.61	$259.60	$259.60
Purchase #3	$21.74	10.776%	$24.0827	$24.08	$24.10	$24.10
Purchase #4	$120.34	5.390%	$126.8263	$126.83	$126.85	$126.80
Purchase #5	$231.33	9.465%	$253.2254	$253.23	$253.25	$253.20
Purchase #6	$131.35	12.748%	$148.0945	$148.09	$148.10	$148.10
Purchase #7	$43.38	4.650%	$45.3972	$45.40	$45.40	$45.40
7 purchase totals =	$862.61		$947.0132	$947.01	$947.05	$947.00