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	$142.35	10.182%	$156.8441	$156.84	$156.85	$156.80
Purchase #2	$134.88	3.648%	$139.8004	$139.80	$139.80	$139.80
Purchase #3	$44.91	12.487%	$50.5179	$50.52	$50.50	$50.50
Purchase #4	$121.51	8.540%	$131.887	$131.89	$131.90	$131.90
Purchase #5	$179.54	10.243%	$197.9303	$197.93	$197.95	$197.90
Purchase #6	$41.39	8.466%	$44.8941	$44.89	$44.90	$44.90
Purchase #7	$244.83	12.871%	$276.3421	$276.34	$276.35	$276.30
7 purchase totals =	$909.41		$998.2159	$998.21	$998.25	$998.10