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	$19.71	3.125%	$20.3259	$20.33	$20.35	$20.30
Purchase #2	$40.63	11.394%	$45.2594	$45.26	$45.25	$45.30
Purchase #3	$146.61	4.240%	$152.8263	$152.83	$152.85	$152.80
Purchase #4	$182.59	3.773%	$189.4791	$189.48	$189.50	$189.50
Purchase #5	$208.82	11.553%	$232.945	$232.95	$232.95	$232.90
Purchase #6	$187.84	6.680%	$200.3877	$200.39	$200.40	$200.40
Purchase #7	$51.60	3.705%	$53.5118	$53.51	$53.50	$53.50
7 purchase totals =	$837.80		$894.7352	$894.75	$894.80	$894.70