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	$244.62	3.773%	$253.8495	$253.85	$253.85	$253.80
Purchase #2	$110.66	10.554%	$122.3391	$122.34	$122.35	$122.30
Purchase #3	$212.90	5.767%	$225.1779	$225.18	$225.20	$225.20
Purchase #4	$18.75	9.166%	$20.4686	$20.47	$20.45	$20.50
Purchase #5	$151.65	13.509%	$172.1364	$172.14	$172.15	$172.10
Purchase #6	$151.57	7.232%	$162.5315	$162.53	$162.55	$162.50
Purchase #7	$95.61	10.290%	$105.4483	$105.45	$105.45	$105.40
7 purchase totals =	$985.76		$1,061.9513	$1,061.96	$1,062.00	$1,061.80