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	$79.71	4.834%	$83.5632	$83.56	$83.55	$83.60
Purchase #2	$92.32	8.742%	$100.3906	$100.39	$100.40	$100.40
Purchase #3	$54.75	8.859%	$59.6003	$59.60	$59.60	$59.60
Purchase #4	$55.37	8.863%	$60.2774	$60.28	$60.30	$60.30
Purchase #5	$87.83	8.845%	$95.5986	$95.60	$95.60	$95.60
Purchase #6	$108.84	4.639%	$113.8891	$113.89	$113.90	$113.90
Purchase #7	$215.74	13.334%	$244.5068	$244.51	$244.50	$244.50
7 purchase totals =	$694.56		$757.8260	$757.83	$757.85	$757.90