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	$71.86	9.699%	$78.8297	$78.83	$78.85	$78.80
Purchase #2	$240.70	13.620%	$273.4833	$273.48	$273.50	$273.50
Purchase #3	$157.78	9.561%	$172.8653	$172.87	$172.85	$172.90
Purchase #4	$231.79	8.137%	$250.6508	$250.65	$250.65	$250.70
Purchase #5	$92.62	5.653%	$97.8558	$97.86	$97.85	$97.90
Purchase #6	$232.46	10.506%	$256.8822	$256.88	$256.90	$256.90
Purchase #7	$224.45	9.517%	$245.8109	$245.81	$245.80	$245.80
7 purchase totals =	$1,251.66		$1,376.3780	$1,376.38	$1,376.40	$1,376.50