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	$137.54	10.186%	$151.5498	$151.55	$151.55	$151.50
Purchase #2	$31.33	10.678%	$34.6754	$34.68	$34.70	$34.70
Purchase #3	$7.26	3.473%	$7.5121	$7.51	$7.50	$7.50
Purchase #4	$133.60	3.788%	$138.6608	$138.66	$138.65	$138.70
Purchase #5	$245.37	12.181%	$275.2585	$275.26	$275.25	$275.30
Purchase #6	$202.56	10.380%	$223.5857	$223.59	$223.60	$223.60
Purchase #7	$113.48	12.215%	$127.3416	$127.34	$127.35	$127.30
7 purchase totals =	$871.14		$958.5839	$958.59	$958.60	$958.60