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	$163.33	3.317%	$168.7477	$168.75	$168.75	$168.70
Purchase #2	$29.39	6.245%	$31.2254	$31.23	$31.25	$31.20
Purchase #3	$37.63	12.622%	$42.3797	$42.38	$42.40	$42.40
Purchase #4	$219.42	10.686%	$242.8672	$242.87	$242.85	$242.90
Purchase #5	$133.31	9.839%	$146.4264	$146.43	$146.45	$146.40
Purchase #6	$130.31	5.765%	$137.8224	$137.82	$137.80	$137.80
Purchase #7	$212.31	6.461%	$226.0273	$226.03	$226.05	$226.00
7 purchase totals =	$925.70		$995.4961	$995.51	$995.55	$995.40