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	$81.67	4.232%	$85.1263	$85.13	$85.15	$85.10
Purchase #2	$205.64	9.574%	$225.328	$225.33	$225.35	$225.30
Purchase #3	$96.74	4.667%	$101.2549	$101.25	$101.25	$101.30
Purchase #4	$121.68	12.565%	$136.9691	$136.97	$136.95	$137.00
Purchase #5	$229.98	4.131%	$239.4805	$239.48	$239.50	$239.50
Purchase #6	$55.69	6.490%	$59.3043	$59.30	$59.30	$59.30
Purchase #7	$90.43	6.159%	$95.9996	$96.00	$96.00	$96.00
7 purchase totals =	$881.83		$943.4627	$943.46	$943.50	$943.50