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	$148.38	5.306%	$156.253	$156.25	$156.25	$156.30
Purchase #2	$29.47	10.547%	$32.5782	$32.58	$32.60	$32.60
Purchase #3	$206.35	12.223%	$231.5722	$231.57	$231.55	$231.60
Purchase #4	$246.55	13.862%	$280.7268	$280.73	$280.75	$280.70
Purchase #5	$16.61	13.394%	$18.8347	$18.83	$18.85	$18.80
Purchase #6	$87.53	4.353%	$91.3402	$91.34	$91.35	$91.30
Purchase #7	$180.33	10.128%	$198.5938	$198.59	$198.60	$198.60
7 purchase totals =	$915.22		$1,009.8989	$1,009.89	$1,009.95	$1,009.90