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	$78.54	4.189%	$81.83	$81.83	$81.85	$81.80
Purchase #2	$87.55	7.585%	$94.1907	$94.19	$94.20	$94.20
Purchase #3	$69.59	4.768%	$72.9081	$72.91	$72.90	$72.90
Purchase #4	$157.28	5.581%	$166.0578	$166.06	$166.05	$166.10
Purchase #5	$143.60	10.687%	$158.9465	$158.95	$158.95	$158.90
Purchase #6	$167.77	4.870%	$175.9404	$175.94	$175.95	$175.90
Purchase #7	$171.63	5.396%	$180.8912	$180.89	$180.90	$180.90
7 purchase totals =	$875.96		$930.7647	$930.77	$930.80	$930.70