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	$121.60	8.827%	$132.3336	$132.33	$132.35	$132.30
Purchase #2	$78.57	6.391%	$83.5914	$83.59	$83.60	$83.60
Purchase #3	$213.53	4.260%	$222.6264	$222.63	$222.65	$222.60
Purchase #4	$122.57	13.520%	$139.1415	$139.14	$139.15	$139.10
Purchase #5	$118.47	5.461%	$124.9396	$124.94	$124.95	$124.90
Purchase #6	$17.43	5.642%	$18.4134	$18.41	$18.40	$18.40
Purchase #7	$150.29	13.787%	$171.0105	$171.01	$171.00	$171.00
7 purchase totals =	$822.46		$892.0564	$892.05	$892.10	$891.90