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	$104.89	7.333%	$112.5816	$112.58	$112.60	$112.60
Purchase #2	$206.82	10.199%	$227.9136	$227.91	$227.90	$227.90
Purchase #3	$74.70	5.604%	$78.8862	$78.89	$78.90	$78.90
Purchase #4	$36.69	3.262%	$37.8868	$37.89	$37.90	$37.90
Purchase #5	$40.55	5.362%	$42.7243	$42.72	$42.70	$42.70
Purchase #6	$27.78	4.545%	$29.0426	$29.04	$29.05	$29.00
Purchase #7	$41.91	3.784%	$43.4959	$43.50	$43.50	$43.50
7 purchase totals =	$533.34		$572.5310	$572.53	$572.55	$572.50