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	$155.46	11.105%	$172.7238	$172.72	$172.70	$172.70
Purchase #2	$71.44	9.316%	$78.0954	$78.10	$78.10	$78.10
Purchase #3	$239.42	11.758%	$267.571	$267.57	$267.55	$267.60
Purchase #4	$51.94	13.287%	$58.8413	$58.84	$58.85	$58.80
Purchase #5	$74.63	4.564%	$78.0361	$78.04	$78.05	$78.00
Purchase #6	$30.51	11.458%	$34.0058	$34.01	$34.00	$34.00
Purchase #7	$172.42	12.233%	$193.5121	$193.51	$193.50	$193.50
7 purchase totals =	$795.82		$882.7855	$882.79	$882.75	$882.70