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	$160.78	5.576%	$169.7451	$169.75	$169.75	$169.70
Purchase #2	$13.63	11.148%	$15.1495	$15.15	$15.15	$15.10
Purchase #3	$136.34	7.756%	$146.9145	$146.91	$146.90	$146.90
Purchase #4	$180.28	11.287%	$200.6282	$200.63	$200.65	$200.60
Purchase #5	$49.76	12.191%	$55.8262	$55.83	$55.85	$55.80
Purchase #6	$196.59	13.338%	$222.8112	$222.81	$222.80	$222.80
Purchase #7	$119.53	10.762%	$132.3938	$132.39	$132.40	$132.40
7 purchase totals =	$856.91		$943.4685	$943.47	$943.50	$943.30