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	$12.69	5.797%	$13.4256	$13.43	$13.45	$13.40
Purchase #2	$233.39	11.171%	$259.462	$259.46	$259.45	$259.50
Purchase #3	$78.67	4.525%	$82.2298	$82.23	$82.25	$82.20
Purchase #4	$148.69	11.705%	$166.0942	$166.09	$166.10	$166.10
Purchase #5	$22.99	11.521%	$25.6387	$25.64	$25.65	$25.60
Purchase #6	$87.36	4.863%	$91.6083	$91.61	$91.60	$91.60
Purchase #7	$116.59	5.184%	$122.634	$122.63	$122.65	$122.60
7 purchase totals =	$700.38		$761.0926	$761.09	$761.15	$761.00