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	$7.38	3.188%	$7.6153	$7.62	$7.60	$7.60
Purchase #2	$6.42	11.529%	$7.1602	$7.16	$7.15	$7.20
Purchase #3	$90.90	6.229%	$96.5622	$96.56	$96.55	$96.60
Purchase #4	$157.96	8.742%	$171.7689	$171.77	$171.75	$171.80
Purchase #5	$98.79	5.313%	$104.0387	$104.04	$104.05	$104.00
Purchase #6	$129.33	9.692%	$141.8647	$141.86	$141.85	$141.90
Purchase #7	$172.58	5.183%	$181.5248	$181.52	$181.50	$181.50
7 purchase totals =	$663.36		$710.5348	$710.53	$710.45	$710.60