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	$67.58	13.726%	$76.856	$76.86	$76.85	$76.90
Purchase #2	$52.58	7.545%	$56.5472	$56.55	$56.55	$56.50
Purchase #3	$43.87	4.678%	$45.9222	$45.92	$45.90	$45.90
Purchase #4	$244.89	4.741%	$256.5002	$256.50	$256.50	$256.50
Purchase #5	$76.41	8.511%	$82.9133	$82.91	$82.90	$82.90
Purchase #6	$44.29	4.593%	$46.3242	$46.32	$46.30	$46.30
Purchase #7	$85.73	9.239%	$93.6506	$93.65	$93.65	$93.70
7 purchase totals =	$615.35		$658.7137	$658.71	$658.65	$658.70