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	$103.46	8.781%	$112.5448	$112.54	$112.55	$112.50
Purchase #2	$196.68	11.294%	$218.893	$218.89	$218.90	$218.90
Purchase #3	$103.67	12.190%	$116.3074	$116.31	$116.30	$116.30
Purchase #4	$124.77	10.547%	$137.9295	$137.93	$137.95	$137.90
Purchase #5	$210.53	10.381%	$232.3851	$232.39	$232.40	$232.40
Purchase #6	$129.81	5.861%	$137.4182	$137.42	$137.40	$137.40
Purchase #7	$44.39	5.349%	$46.7644	$46.76	$46.75	$46.80
7 purchase totals =	$913.31		$1,002.2424	$1,002.24	$1,002.25	$1,002.20