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	$218.27	5.835%	$231.0061	$231.01	$231.00	$231.00
Purchase #2	$151.96	11.816%	$169.9156	$169.92	$169.90	$169.90
Purchase #3	$185.92	7.796%	$200.4143	$200.41	$200.40	$200.40
Purchase #4	$121.40	3.453%	$125.5919	$125.59	$125.60	$125.60
Purchase #5	$136.77	13.620%	$155.3981	$155.40	$155.40	$155.40
Purchase #6	$28.78	8.111%	$31.1143	$31.11	$31.10	$31.10
Purchase #7	$208.54	13.864%	$237.452	$237.45	$237.45	$237.50
7 purchase totals =	$1,051.64		$1,150.8923	$1,150.89	$1,150.85	$1,150.90