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	$125.27	4.862%	$131.3606	$131.36	$131.35	$131.40
Purchase #2	$113.33	9.127%	$123.6736	$123.67	$123.65	$123.70
Purchase #3	$157.58	7.420%	$169.2724	$169.27	$169.25	$169.30
Purchase #4	$235.45	11.531%	$262.5997	$262.60	$262.60	$262.60
Purchase #5	$166.46	3.380%	$172.0863	$172.09	$172.10	$172.10
Purchase #6	$162.44	10.420%	$179.3662	$179.37	$179.35	$179.40
Purchase #7	$15.28	10.643%	$16.9063	$16.91	$16.90	$16.90
7 purchase totals =	$975.81		$1,055.2651	$1,055.27	$1,055.20	$1,055.40