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	$162.52	7.162%	$174.1597	$174.16	$174.15	$174.20
Purchase #2	$48.54	4.208%	$50.5826	$50.58	$50.60	$50.60
Purchase #3	$45.84	9.784%	$50.325	$50.33	$50.35	$50.30
Purchase #4	$77.76	13.697%	$88.4108	$88.41	$88.40	$88.40
Purchase #5	$40.85	9.574%	$44.761	$44.76	$44.75	$44.80
Purchase #6	$42.31	8.373%	$45.8526	$45.85	$45.85	$45.90
Purchase #7	$186.47	11.828%	$208.5257	$208.53	$208.55	$208.50
7 purchase totals =	$604.29		$662.6174	$662.62	$662.65	$662.70