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	$116.39	6.554%	$124.0182	$124.02	$124.00	$124.00
Purchase #2	$130.90	10.232%	$144.2937	$144.29	$144.30	$144.30
Purchase #3	$175.90	13.381%	$199.4372	$199.44	$199.45	$199.40
Purchase #4	$104.46	6.601%	$111.3554	$111.36	$111.35	$111.40
Purchase #5	$44.90	12.164%	$50.3616	$50.36	$50.35	$50.40
Purchase #6	$20.99	3.212%	$21.6642	$21.66	$21.65	$21.70
Purchase #7	$67.38	5.510%	$71.0926	$71.09	$71.10	$71.10
7 purchase totals =	$660.92		$722.2229	$722.22	$722.20	$722.30