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	$111.80	12.834%	$126.1484	$126.15	$126.15	$126.10
Purchase #2	$138.93	6.451%	$147.8924	$147.89	$147.90	$147.90
Purchase #3	$134.59	13.290%	$152.477	$152.48	$152.50	$152.50
Purchase #4	$218.32	10.849%	$242.0055	$242.01	$242.00	$242.00
Purchase #5	$21.87	12.345%	$24.5699	$24.57	$24.55	$24.60
Purchase #6	$106.68	10.318%	$117.6872	$117.69	$117.70	$117.70
Purchase #7	$216.71	10.215%	$238.8469	$238.85	$238.85	$238.80
7 purchase totals =	$948.90		$1,049.6273	$1,049.64	$1,049.65	$1,049.60