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	$130.27	10.815%	$144.3587	$144.36	$144.35	$144.40
Purchase #2	$40.90	9.866%	$44.9352	$44.94	$44.95	$44.90
Purchase #3	$243.41	6.375%	$258.9274	$258.93	$258.95	$258.90
Purchase #4	$42.55	7.436%	$45.714	$45.71	$45.70	$45.70
Purchase #5	$208.51	4.570%	$218.0389	$218.04	$218.05	$218.00
Purchase #6	$124.28	8.575%	$134.937	$134.94	$134.95	$134.90
Purchase #7	$40.44	12.427%	$45.4655	$45.47	$45.45	$45.50
7 purchase totals =	$830.36		$892.3767	$892.39	$892.40	$892.30