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	$102.65	9.690%	$112.5968	$112.60	$112.60	$112.60
Purchase #2	$120.61	4.449%	$125.9759	$125.98	$126.00	$126.00
Purchase #3	$146.81	12.642%	$165.3697	$165.37	$165.35	$165.40
Purchase #4	$13.32	10.567%	$14.7275	$14.73	$14.75	$14.70
Purchase #5	$116.43	9.769%	$127.804	$127.80	$127.80	$127.80
Purchase #6	$170.72	13.342%	$193.4975	$193.50	$193.50	$193.50
Purchase #7	$159.72	12.391%	$179.5109	$179.51	$179.50	$179.50
7 purchase totals =	$830.26		$919.4823	$919.49	$919.50	$919.50