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	$163.56	3.343%	$169.0278	$169.03	$169.05	$169.00
Purchase #2	$77.55	12.839%	$87.5066	$87.51	$87.50	$87.50
Purchase #3	$38.45	10.389%	$42.4446	$42.44	$42.45	$42.40
Purchase #4	$95.84	8.587%	$104.0698	$104.07	$104.05	$104.10
Purchase #5	$76.43	3.215%	$78.8872	$78.89	$78.90	$78.90
Purchase #6	$200.29	10.145%	$220.6094	$220.61	$220.60	$220.60
Purchase #7	$7.65	6.173%	$8.1222	$8.12	$8.10	$8.10
7 purchase totals =	$659.77		$710.6676	$710.67	$710.65	$710.60