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	$174.53	8.760%	$189.8188	$189.82	$189.80	$189.80
Purchase #2	$134.94	4.522%	$141.042	$141.04	$141.05	$141.00
Purchase #3	$43.61	11.475%	$48.6142	$48.61	$48.60	$48.60
Purchase #4	$42.48	4.185%	$44.2578	$44.26	$44.25	$44.30
Purchase #5	$53.94	3.152%	$55.6402	$55.64	$55.65	$55.60
Purchase #6	$141.77	3.554%	$146.8085	$146.81	$146.80	$146.80
Purchase #7	$176.35	11.327%	$196.3252	$196.33	$196.35	$196.30
7 purchase totals =	$767.62		$822.5067	$822.51	$822.50	$822.40