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	$40.27	8.172%	$43.5609	$43.56	$43.55	$43.60
Purchase #2	$212.93	3.128%	$219.5905	$219.59	$219.60	$219.60
Purchase #3	$32.39	3.314%	$33.4634	$33.46	$33.45	$33.50
Purchase #4	$146.30	12.548%	$164.6577	$164.66	$164.65	$164.70
Purchase #5	$78.71	11.810%	$88.0057	$88.01	$88.00	$88.00
Purchase #6	$36.90	3.569%	$38.217	$38.22	$38.20	$38.20
Purchase #7	$233.49	6.204%	$247.9757	$247.98	$248.00	$248.00
7 purchase totals =	$780.99		$835.4709	$835.48	$835.45	$835.60