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	$46.89	3.169%	$48.3759	$48.38	$48.40	$48.40
Purchase #2	$32.39	11.451%	$36.099	$36.10	$36.10	$36.10
Purchase #3	$53.94	3.576%	$55.8689	$55.87	$55.85	$55.90
Purchase #4	$42.46	13.351%	$48.1288	$48.13	$48.15	$48.10
Purchase #5	$18.36	11.363%	$20.4462	$20.45	$20.45	$20.40
Purchase #6	$31.26	5.341%	$32.9296	$32.93	$32.95	$32.90
Purchase #7	$138.38	13.554%	$157.136	$157.14	$157.15	$157.10
7 purchase totals =	$363.68		$398.9844	$399.00	$399.05	$398.90