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	$189.82	5.390%	$200.0513	$200.05	$200.05	$200.10
Purchase #2	$200.65	13.374%	$227.4849	$227.48	$227.50	$227.50
Purchase #3	$107.54	3.340%	$111.1318	$111.13	$111.15	$111.10
Purchase #4	$216.85	8.185%	$234.5992	$234.60	$234.60	$234.60
Purchase #5	$81.63	4.180%	$85.0421	$85.04	$85.05	$85.00
Purchase #6	$43.97	10.790%	$48.7144	$48.71	$48.70	$48.70
Purchase #7	$136.25	5.828%	$144.1907	$144.19	$144.20	$144.20
7 purchase totals =	$976.71		$1,051.2144	$1,051.20	$1,051.25	$1,051.20