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	$167.34	10.561%	$185.0128	$185.01	$185.00	$185.00
Purchase #2	$175.58	8.531%	$190.5587	$190.56	$190.55	$190.60
Purchase #3	$54.38	8.559%	$59.0344	$59.03	$59.05	$59.00
Purchase #4	$177.87	12.392%	$199.9117	$199.91	$199.90	$199.90
Purchase #5	$105.60	12.515%	$118.8158	$118.82	$118.80	$118.80
Purchase #6	$122.61	4.407%	$128.0134	$128.01	$128.00	$128.00
Purchase #7	$13.49	10.385%	$14.8909	$14.89	$14.90	$14.90
7 purchase totals =	$816.87		$896.2377	$896.23	$896.20	$896.20