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	$193.71	7.664%	$208.5559	$208.56	$208.55	$208.60
Purchase #2	$236.53	11.279%	$263.2082	$263.21	$263.20	$263.20
Purchase #3	$220.83	5.452%	$232.8697	$232.87	$232.85	$232.90
Purchase #4	$131.49	9.548%	$144.0447	$144.04	$144.05	$144.00
Purchase #5	$172.72	7.450%	$185.5876	$185.59	$185.60	$185.60
Purchase #6	$193.38	7.830%	$208.5217	$208.52	$208.50	$208.50
Purchase #7	$71.58	10.173%	$78.8618	$78.86	$78.85	$78.90
7 purchase totals =	$1,220.24		$1,321.6496	$1,321.65	$1,321.60	$1,321.70