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	$79.81	3.671%	$82.7398	$82.74	$82.75	$82.70
Purchase #2	$187.64	13.831%	$213.5925	$213.59	$213.60	$213.60
Purchase #3	$17.33	8.194%	$18.75	$18.75	$18.75	$18.80
Purchase #4	$38.97	11.526%	$43.4617	$43.46	$43.45	$43.50
Purchase #5	$157.37	11.709%	$175.7965	$175.80	$175.80	$175.80
Purchase #6	$52.86	11.870%	$59.1345	$59.13	$59.15	$59.10
Purchase #7	$29.99	5.530%	$31.6484	$31.65	$31.65	$31.60
7 purchase totals =	$563.97		$625.1234	$625.12	$625.15	$625.10