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	$81.57	5.249%	$85.8516	$85.85	$85.85	$85.90
Purchase #2	$183.74	9.165%	$200.5798	$200.58	$200.60	$200.60
Purchase #3	$30.43	4.614%	$31.834	$31.83	$31.85	$31.80
Purchase #4	$82.33	3.275%	$85.0263	$85.03	$85.05	$85.00
Purchase #5	$78.88	5.138%	$82.9329	$82.93	$82.95	$82.90
Purchase #6	$60.87	6.181%	$64.6324	$64.63	$64.65	$64.60
Purchase #7	$193.82	13.841%	$220.6466	$220.65	$220.65	$220.60
7 purchase totals =	$711.64		$771.5036	$771.50	$771.60	$771.40