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	$75.78	12.709%	$85.4109	$85.41	$85.40	$85.40
Purchase #2	$238.65	4.314%	$248.9454	$248.95	$248.95	$248.90
Purchase #3	$52.41	9.266%	$57.2663	$57.27	$57.25	$57.30
Purchase #4	$94.29	4.544%	$98.5745	$98.57	$98.55	$98.60
Purchase #5	$104.71	13.451%	$118.7945	$118.79	$118.80	$118.80
Purchase #6	$97.36	5.807%	$103.0137	$103.01	$103.00	$103.00
Purchase #7	$90.83	10.569%	$100.4298	$100.43	$100.45	$100.40
7 purchase totals =	$754.03		$812.4351	$812.43	$812.40	$812.40