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	$241.76	8.718%	$262.8366	$262.84	$262.85	$262.80
Purchase #2	$164.33	12.317%	$184.5705	$184.57	$184.55	$184.60
Purchase #3	$93.63	13.646%	$106.4067	$106.41	$106.40	$106.40
Purchase #4	$90.34	5.583%	$95.3837	$95.38	$95.40	$95.40
Purchase #5	$9.46	8.563%	$10.2701	$10.27	$10.25	$10.30
Purchase #6	$244.59	4.330%	$255.1807	$255.18	$255.20	$255.20
Purchase #7	$56.66	13.453%	$64.2825	$64.28	$64.30	$64.30
7 purchase totals =	$900.77		$978.9308	$978.93	$978.95	$979.00