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	$114.87	13.260%	$130.1018	$130.10	$130.10	$130.10
Purchase #2	$126.89	8.647%	$137.8622	$137.86	$137.85	$137.90
Purchase #3	$66.60	8.157%	$72.0326	$72.03	$72.05	$72.00
Purchase #4	$45.34	7.709%	$48.8353	$48.84	$48.85	$48.80
Purchase #5	$234.44	4.831%	$245.7658	$245.77	$245.75	$245.80
Purchase #6	$43.25	5.385%	$45.579	$45.58	$45.60	$45.60
Purchase #7	$203.71	12.569%	$229.3143	$229.31	$229.30	$229.30
7 purchase totals =	$835.10		$909.4910	$909.49	$909.50	$909.50