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	$125.58	5.782%	$132.841	$132.84	$132.85	$132.80
Purchase #2	$69.34	12.485%	$77.9971	$78.00	$78.00	$78.00
Purchase #3	$206.26	9.310%	$225.4628	$225.46	$225.45	$225.50
Purchase #4	$126.50	4.576%	$132.2886	$132.29	$132.30	$132.30
Purchase #5	$45.43	9.653%	$49.8154	$49.82	$49.80	$49.80
Purchase #6	$114.63	3.680%	$118.8484	$118.85	$118.85	$118.80
Purchase #7	$113.98	11.829%	$127.4627	$127.46	$127.45	$127.50
7 purchase totals =	$801.72		$864.7160	$864.72	$864.70	$864.70