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	$208.51	6.671%	$222.4197	$222.42	$222.40	$222.40
Purchase #2	$245.42	4.581%	$256.6627	$256.66	$256.65	$256.70
Purchase #3	$37.97	13.326%	$43.0299	$43.03	$43.05	$43.00
Purchase #4	$149.48	3.246%	$154.3321	$154.33	$154.35	$154.30
Purchase #5	$114.34	8.460%	$124.0132	$124.01	$124.00	$124.00
Purchase #6	$38.82	10.218%	$42.7866	$42.79	$42.80	$42.80
Purchase #7	$237.43	9.519%	$260.031	$260.03	$260.05	$260.00
7 purchase totals =	$1,031.97		$1,103.2752	$1,103.27	$1,103.30	$1,103.20