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	$228.73	3.384%	$236.4702	$236.47	$236.45	$236.50
Purchase #2	$97.33	8.853%	$105.9466	$105.95	$105.95	$105.90
Purchase #3	$19.80	5.856%	$20.9595	$20.96	$20.95	$21.00
Purchase #4	$47.44	7.137%	$50.8258	$50.83	$50.85	$50.80
Purchase #5	$39.61	6.482%	$42.1775	$42.18	$42.20	$42.20
Purchase #6	$30.88	8.526%	$33.5128	$33.51	$33.50	$33.50
Purchase #7	$7.43	10.594%	$8.2171	$8.22	$8.20	$8.20
7 purchase totals =	$471.22		$498.1095	$498.12	$498.10	$498.10