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	$87.45	6.185%	$92.8588	$92.86	$92.85	$92.90
Purchase #2	$64.75	4.249%	$67.5012	$67.50	$67.50	$67.50
Purchase #3	$242.49	5.404%	$255.5942	$255.59	$255.60	$255.60
Purchase #4	$58.63	13.820%	$66.7327	$66.73	$66.75	$66.70
Purchase #5	$28.87	7.732%	$31.1022	$31.10	$31.10	$31.10
Purchase #6	$238.86	4.556%	$249.7425	$249.74	$249.75	$249.70
Purchase #7	$139.85	10.166%	$154.0672	$154.07	$154.05	$154.10
7 purchase totals =	$860.90		$917.5988	$917.59	$917.60	$917.60