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	$20.37	12.252%	$22.8657	$22.87	$22.85	$22.90
Purchase #2	$23.53	7.313%	$25.2507	$25.25	$25.25	$25.30
Purchase #3	$78.95	4.820%	$82.7554	$82.76	$82.75	$82.80
Purchase #4	$225.65	9.287%	$246.6061	$246.61	$246.60	$246.60
Purchase #5	$149.96	11.614%	$167.3764	$167.38	$167.40	$167.40
Purchase #6	$139.72	11.105%	$155.2359	$155.24	$155.25	$155.20
Purchase #7	$118.98	7.519%	$127.9261	$127.93	$127.95	$127.90
7 purchase totals =	$757.16		$828.0163	$828.04	$828.05	$828.10