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	$192.66	13.412%	$218.4996	$218.50	$218.50	$218.50
Purchase #2	$13.34	11.326%	$14.8509	$14.85	$14.85	$14.90
Purchase #3	$101.85	10.508%	$112.5524	$112.55	$112.55	$112.60
Purchase #4	$100.51	5.631%	$106.1697	$106.17	$106.15	$106.20
Purchase #5	$246.35	11.847%	$275.5351	$275.54	$275.55	$275.50
Purchase #6	$77.48	12.146%	$86.8907	$86.89	$86.90	$86.90
Purchase #7	$82.74	9.297%	$90.4323	$90.43	$90.45	$90.40
7 purchase totals =	$814.93		$904.9307	$904.93	$904.95	$905.00