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	$57.33	11.489%	$63.9166	$63.92	$63.90	$63.90
Purchase #2	$127.51	3.249%	$131.6528	$131.65	$131.65	$131.70
Purchase #3	$60.73	11.394%	$67.6496	$67.65	$67.65	$67.60
Purchase #4	$111.90	8.395%	$121.294	$121.29	$121.30	$121.30
Purchase #5	$159.71	11.535%	$178.1325	$178.13	$178.15	$178.10
Purchase #6	$98.91	12.230%	$111.0067	$111.01	$111.00	$111.00
Purchase #7	$118.37	10.569%	$130.8805	$130.88	$130.90	$130.90
7 purchase totals =	$734.46		$804.5327	$804.53	$804.55	$804.50