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	$172.76	4.455%	$180.4565	$180.46	$180.45	$180.50
Purchase #2	$65.81	10.752%	$72.8859	$72.89	$72.90	$72.90
Purchase #3	$202.96	8.296%	$219.7976	$219.80	$219.80	$219.80
Purchase #4	$20.43	3.359%	$21.1162	$21.12	$21.10	$21.10
Purchase #5	$208.57	6.572%	$222.2772	$222.28	$222.30	$222.30
Purchase #6	$169.51	3.242%	$175.0055	$175.01	$175.00	$175.00
Purchase #7	$52.32	11.483%	$58.3279	$58.33	$58.35	$58.30
7 purchase totals =	$892.36		$949.8668	$949.89	$949.90	$949.90