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	$145.36	5.608%	$153.5118	$153.51	$153.50	$153.50
Purchase #2	$63.89	4.189%	$66.5664	$66.57	$66.55	$66.60
Purchase #3	$108.73	4.627%	$113.7609	$113.76	$113.75	$113.80
Purchase #4	$197.39	6.214%	$209.6558	$209.66	$209.65	$209.70
Purchase #5	$40.52	13.107%	$45.831	$45.83	$45.85	$45.80
Purchase #6	$162.72	5.231%	$171.2319	$171.23	$171.25	$171.20
Purchase #7	$123.64	11.515%	$137.8771	$137.88	$137.90	$137.90
7 purchase totals =	$842.25		$898.4349	$898.44	$898.45	$898.50