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	$51.44	8.513%	$55.8191	$55.82	$55.80	$55.80
Purchase #2	$131.32	11.596%	$146.5479	$146.55	$146.55	$146.50
Purchase #3	$223.45	9.110%	$243.8063	$243.81	$243.80	$243.80
Purchase #4	$171.94	6.778%	$183.5941	$183.59	$183.60	$183.60
Purchase #5	$176.50	8.173%	$190.9253	$190.93	$190.95	$190.90
Purchase #6	$53.52	3.152%	$55.207	$55.21	$55.20	$55.20
Purchase #7	$17.25	7.670%	$18.5731	$18.57	$18.55	$18.60
7 purchase totals =	$825.42		$894.4728	$894.48	$894.45	$894.40