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	$36.62	12.751%	$41.2894	$41.29	$41.30	$41.30
Purchase #2	$26.39	4.669%	$27.6221	$27.62	$27.60	$27.60
Purchase #3	$87.72	8.308%	$95.0078	$95.01	$95.00	$95.00
Purchase #4	$10.30	7.322%	$11.0542	$11.05	$11.05	$11.10
Purchase #5	$131.84	9.548%	$144.4281	$144.43	$144.45	$144.40
Purchase #6	$20.89	3.130%	$21.5439	$21.54	$21.55	$21.50
Purchase #7	$18.97	7.362%	$20.3666	$20.37	$20.35	$20.40
7 purchase totals =	$332.73		$361.3121	$361.31	$361.30	$361.30