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	$219.77	12.163%	$246.5006	$246.50	$246.50	$246.50
Purchase #2	$161.92	4.746%	$169.6047	$169.60	$169.60	$169.60
Purchase #3	$68.92	4.791%	$72.222	$72.22	$72.20	$72.20
Purchase #4	$196.71	13.761%	$223.7793	$223.78	$223.80	$223.80
Purchase #5	$232.30	7.458%	$249.6249	$249.62	$249.60	$249.60
Purchase #6	$132.86	13.130%	$150.3045	$150.30	$150.30	$150.30
Purchase #7	$196.66	3.443%	$203.431	$203.43	$203.45	$203.40
7 purchase totals =	$1,209.14		$1,315.4670	$1,315.45	$1,315.45	$1,315.40