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	$157.58	4.359%	$164.4489	$164.45	$164.45	$164.40
Purchase #2	$39.83	7.793%	$42.934	$42.93	$42.95	$42.90
Purchase #3	$32.96	5.562%	$34.7932	$34.79	$34.80	$34.80
Purchase #4	$139.98	10.569%	$154.7745	$154.77	$154.75	$154.80
Purchase #5	$147.75	7.569%	$158.9332	$158.93	$158.95	$158.90
Purchase #6	$117.75	5.105%	$123.7611	$123.76	$123.75	$123.80
Purchase #7	$243.68	12.162%	$273.3164	$273.32	$273.30	$273.30
7 purchase totals =	$879.53		$952.9613	$952.95	$952.95	$952.90