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	$139.84	5.471%	$147.4906	$147.49	$147.50	$147.50
Purchase #2	$166.26	3.519%	$172.1107	$172.11	$172.10	$172.10
Purchase #3	$11.37	4.197%	$11.8472	$11.85	$11.85	$11.80
Purchase #4	$84.26	13.441%	$95.5854	$95.59	$95.60	$95.60
Purchase #5	$103.72	12.333%	$116.5118	$116.51	$116.50	$116.50
Purchase #6	$67.64	7.324%	$72.594	$72.59	$72.60	$72.60
Purchase #7	$112.85	5.610%	$119.1809	$119.18	$119.20	$119.20
7 purchase totals =	$685.94		$735.3206	$735.32	$735.35	$735.30