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	$59.86	13.361%	$67.8579	$67.86	$67.85	$67.90
Purchase #2	$76.85	5.444%	$81.0337	$81.03	$81.05	$81.00
Purchase #3	$240.83	10.275%	$265.5753	$265.58	$265.60	$265.60
Purchase #4	$32.79	11.802%	$36.6599	$36.66	$36.65	$36.70
Purchase #5	$37.78	4.855%	$39.6142	$39.61	$39.60	$39.60
Purchase #6	$119.91	9.603%	$131.425	$131.43	$131.45	$131.40
Purchase #7	$127.74	12.172%	$143.2885	$143.29	$143.30	$143.30
7 purchase totals =	$695.76		$765.4545	$765.46	$765.50	$765.50