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	$43.34	11.870%	$48.4845	$48.48	$48.50	$48.50
Purchase #2	$6.73	7.826%	$7.2567	$7.26	$7.25	$7.30
Purchase #3	$29.85	5.630%	$31.5306	$31.53	$31.55	$31.50
Purchase #4	$169.56	12.617%	$190.9534	$190.95	$190.95	$191.00
Purchase #5	$165.79	9.122%	$180.9134	$180.91	$180.90	$180.90
Purchase #6	$56.44	5.720%	$59.6684	$59.67	$59.65	$59.70
Purchase #7	$122.51	13.111%	$138.5723	$138.57	$138.55	$138.60
7 purchase totals =	$594.22		$657.3793	$657.37	$657.35	$657.50