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	$194.87	7.848%	$210.1634	$210.16	$210.15	$210.20
Purchase #2	$103.37	8.302%	$111.9518	$111.95	$111.95	$112.00
Purchase #3	$190.53	3.372%	$196.9547	$196.95	$196.95	$197.00
Purchase #4	$137.72	12.349%	$154.727	$154.73	$154.75	$154.70
Purchase #5	$81.42	4.754%	$85.2907	$85.29	$85.30	$85.30
Purchase #6	$38.53	10.547%	$42.5938	$42.59	$42.60	$42.60
Purchase #7	$40.49	5.380%	$42.6684	$42.67	$42.65	$42.70
7 purchase totals =	$786.93		$844.3498	$844.34	$844.35	$844.50