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	$246.31	3.852%	$255.7979	$255.80	$255.80	$255.80
Purchase #2	$30.66	9.680%	$33.6279	$33.63	$33.65	$33.60
Purchase #3	$108.70	7.294%	$116.6286	$116.63	$116.65	$116.60
Purchase #4	$54.78	8.170%	$59.2555	$59.26	$59.25	$59.30
Purchase #5	$220.96	8.835%	$240.4818	$240.48	$240.50	$240.50
Purchase #6	$164.82	13.859%	$187.6624	$187.66	$187.65	$187.70
Purchase #7	$41.52	6.673%	$44.2906	$44.29	$44.30	$44.30
7 purchase totals =	$867.75		$937.7447	$937.75	$937.80	$937.80