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	$192.79	4.157%	$200.8043	$200.80	$200.80	$200.80
Purchase #2	$186.59	11.793%	$208.5946	$208.59	$208.60	$208.60
Purchase #3	$46.77	13.392%	$53.0334	$53.03	$53.05	$53.00
Purchase #4	$221.33	11.853%	$247.5642	$247.56	$247.55	$247.60
Purchase #5	$130.29	10.522%	$143.9991	$144.00	$144.00	$144.00
Purchase #6	$67.58	12.640%	$76.1221	$76.12	$76.10	$76.10
Purchase #7	$54.84	8.173%	$59.3221	$59.32	$59.30	$59.30
7 purchase totals =	$900.19		$989.4398	$989.42	$989.40	$989.40