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	$132.63	10.226%	$146.1927	$146.19	$146.20	$146.20
Purchase #2	$215.61	13.143%	$243.9476	$243.95	$243.95	$243.90
Purchase #3	$71.59	9.134%	$78.129	$78.13	$78.15	$78.10
Purchase #4	$10.94	3.386%	$11.3104	$11.31	$11.30	$11.30
Purchase #5	$221.31	7.634%	$238.2048	$238.20	$238.20	$238.20
Purchase #6	$237.55	5.849%	$251.4443	$251.44	$251.45	$251.40
Purchase #7	$31.86	4.763%	$33.3775	$33.38	$33.40	$33.40
7 purchase totals =	$921.49		$1,002.6063	$1,002.60	$1,002.65	$1,002.50