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	$123.67	7.222%	$132.6014	$132.60	$132.60	$132.60
Purchase #2	$215.91	5.264%	$227.2755	$227.28	$227.30	$227.30
Purchase #3	$168.96	9.718%	$185.3795	$185.38	$185.40	$185.40
Purchase #4	$80.25	11.769%	$89.6946	$89.69	$89.70	$89.70
Purchase #5	$189.44	12.718%	$213.533	$213.53	$213.55	$213.50
Purchase #6	$217.54	12.649%	$245.0566	$245.06	$245.05	$245.10
Purchase #7	$137.86	4.173%	$143.6129	$143.61	$143.60	$143.60
7 purchase totals =	$1,133.63		$1,237.1535	$1,237.15	$1,237.20	$1,237.20