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	$38.83	13.690%	$44.1458	$44.15	$44.15	$44.10
Purchase #2	$128.86	13.320%	$146.0242	$146.02	$146.00	$146.00
Purchase #3	$65.39	8.416%	$70.8932	$70.89	$70.90	$70.90
Purchase #4	$107.80	3.841%	$111.9406	$111.94	$111.95	$111.90
Purchase #5	$112.58	9.542%	$123.3224	$123.32	$123.30	$123.30
Purchase #6	$218.69	3.136%	$225.5481	$225.55	$225.55	$225.50
Purchase #7	$179.80	8.533%	$195.1423	$195.14	$195.15	$195.10
7 purchase totals =	$851.95		$917.0166	$917.01	$917.00	$916.80