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	$115.46	9.653%	$126.6054	$126.61	$126.60	$126.60
Purchase #2	$59.45	11.218%	$66.1191	$66.12	$66.10	$66.10
Purchase #3	$147.71	7.395%	$158.6332	$158.63	$158.65	$158.60
Purchase #4	$31.39	6.675%	$33.4853	$33.49	$33.50	$33.50
Purchase #5	$10.55	7.495%	$11.3407	$11.34	$11.35	$11.30
Purchase #6	$27.78	12.300%	$31.1969	$31.20	$31.20	$31.20
Purchase #7	$64.30	13.532%	$73.0011	$73.00	$73.00	$73.00
7 purchase totals =	$456.64		$500.3817	$500.39	$500.40	$500.30