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	$220.50	8.151%	$238.473	$238.47	$238.45	$238.50
Purchase #2	$115.50	13.503%	$131.096	$131.10	$131.10	$131.10
Purchase #3	$50.29	9.549%	$55.0922	$55.09	$55.10	$55.10
Purchase #4	$61.85	11.807%	$69.1526	$69.15	$69.15	$69.20
Purchase #5	$148.55	7.641%	$159.9007	$159.90	$159.90	$159.90
Purchase #6	$198.57	5.282%	$209.0585	$209.06	$209.05	$209.10
Purchase #7	$157.41	11.492%	$175.4996	$175.50	$175.50	$175.50
7 purchase totals =	$952.67		$1,038.2726	$1,038.27	$1,038.25	$1,038.40