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	$10.72	3.858%	$11.1336	$11.13	$11.15	$11.10
Purchase #2	$167.80	13.544%	$190.5268	$190.53	$190.55	$190.50
Purchase #3	$5.66	10.449%	$6.2514	$6.25	$6.25	$6.30
Purchase #4	$14.85	5.459%	$15.6607	$15.66	$15.65	$15.70
Purchase #5	$53.58	12.219%	$60.1269	$60.13	$60.15	$60.10
Purchase #6	$110.34	6.781%	$117.8222	$117.82	$117.80	$117.80
Purchase #7	$37.52	12.190%	$42.0937	$42.09	$42.10	$42.10
7 purchase totals =	$400.47		$443.6153	$443.61	$443.65	$443.60