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	$134.39	13.707%	$152.8108	$152.81	$152.80	$152.80
Purchase #2	$35.88	11.472%	$39.9962	$40.00	$40.00	$40.00
Purchase #3	$30.43	3.336%	$31.4451	$31.45	$31.45	$31.40
Purchase #4	$208.56	4.865%	$218.7064	$218.71	$218.70	$218.70
Purchase #5	$87.77	9.642%	$96.2328	$96.23	$96.25	$96.20
Purchase #6	$9.59	6.839%	$10.2459	$10.25	$10.25	$10.20
Purchase #7	$111.69	10.572%	$123.4979	$123.50	$123.50	$123.50
7 purchase totals =	$618.31		$672.9351	$672.95	$672.95	$672.80