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	$212.55	5.143%	$223.4814	$223.48	$223.50	$223.50
Purchase #2	$213.89	13.384%	$242.517	$242.52	$242.50	$242.50
Purchase #3	$130.76	10.728%	$144.7879	$144.79	$144.80	$144.80
Purchase #4	$220.48	6.131%	$233.9976	$234.00	$234.00	$234.00
Purchase #5	$43.58	4.490%	$45.5367	$45.54	$45.55	$45.50
Purchase #6	$74.38	13.693%	$84.5649	$84.56	$84.55	$84.60
Purchase #7	$80.99	8.164%	$87.602	$87.60	$87.60	$87.60
7 purchase totals =	$976.63		$1,062.4875	$1,062.49	$1,062.50	$1,062.50