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	$62.52	8.761%	$67.9974	$68.00	$68.00	$68.00
Purchase #2	$51.28	9.853%	$56.3326	$56.33	$56.35	$56.30
Purchase #3	$132.49	5.285%	$139.4921	$139.49	$139.50	$139.50
Purchase #4	$55.63	7.680%	$59.9024	$59.90	$59.90	$59.90
Purchase #5	$53.55	4.317%	$55.8618	$55.86	$55.85	$55.90
Purchase #6	$30.31	9.744%	$33.2634	$33.26	$33.25	$33.30
Purchase #7	$18.84	4.389%	$19.6669	$19.67	$19.65	$19.70
7 purchase totals =	$404.62		$432.5166	$432.51	$432.50	$432.60