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	$230.86	13.759%	$262.624	$262.62	$262.60	$262.60
Purchase #2	$147.52	3.179%	$152.2097	$152.21	$152.20	$152.20
Purchase #3	$217.98	3.417%	$225.4284	$225.43	$225.45	$225.40
Purchase #4	$199.34	9.606%	$218.4886	$218.49	$218.50	$218.50
Purchase #5	$108.44	9.535%	$118.7798	$118.78	$118.80	$118.80
Purchase #6	$59.40	7.455%	$63.8283	$63.83	$63.85	$63.80
Purchase #7	$35.76	13.797%	$40.6938	$40.69	$40.70	$40.70
7 purchase totals =	$999.30		$1,082.0526	$1,082.05	$1,082.10	$1,082.00