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	$214.34	6.205%	$227.6398	$227.64	$227.65	$227.60
Purchase #2	$72.38	13.376%	$82.0615	$82.06	$82.05	$82.10
Purchase #3	$78.66	10.736%	$87.1049	$87.10	$87.10	$87.10
Purchase #4	$80.87	8.284%	$87.5693	$87.57	$87.55	$87.60
Purchase #5	$213.67	11.581%	$238.4151	$238.42	$238.40	$238.40
Purchase #6	$244.34	10.868%	$270.8949	$270.89	$270.90	$270.90
Purchase #7	$132.25	12.353%	$148.5868	$148.59	$148.60	$148.60
7 purchase totals =	$1,036.51		$1,142.2723	$1,142.27	$1,142.25	$1,142.30