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	$118.34	4.469%	$123.6286	$123.63	$123.65	$123.60
Purchase #2	$67.96	3.659%	$70.4467	$70.45	$70.45	$70.40
Purchase #3	$87.61	12.812%	$98.8346	$98.83	$98.85	$98.80
Purchase #4	$192.75	12.503%	$216.8495	$216.85	$216.85	$216.80
Purchase #5	$51.60	8.777%	$56.1289	$56.13	$56.15	$56.10
Purchase #6	$136.75	11.530%	$152.5173	$152.52	$152.50	$152.50
Purchase #7	$107.74	8.186%	$116.5596	$116.56	$116.55	$116.60
7 purchase totals =	$762.75		$834.9652	$834.97	$835.00	$834.80