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	$133.64	5.513%	$141.0076	$141.01	$141.00	$141.00
Purchase #2	$174.42	9.289%	$190.6219	$190.62	$190.60	$190.60
Purchase #3	$206.36	8.480%	$223.8593	$223.86	$223.85	$223.90
Purchase #4	$141.61	4.792%	$148.396	$148.40	$148.40	$148.40
Purchase #5	$49.80	4.754%	$52.1675	$52.17	$52.15	$52.20
Purchase #6	$14.37	11.623%	$16.0402	$16.04	$16.05	$16.00
Purchase #7	$153.39	12.688%	$172.8521	$172.85	$172.85	$172.90
7 purchase totals =	$873.59		$944.9446	$944.95	$944.90	$945.00