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	$72.85	4.347%	$76.0168	$76.02	$76.00	$76.00
Purchase #2	$220.96	9.835%	$242.6914	$242.69	$242.70	$242.70
Purchase #3	$38.61	11.470%	$43.0386	$43.04	$43.05	$43.00
Purchase #4	$246.58	13.159%	$279.0275	$279.03	$279.05	$279.00
Purchase #5	$196.66	9.417%	$215.1795	$215.18	$215.20	$215.20
Purchase #6	$151.99	10.505%	$167.9565	$167.96	$167.95	$168.00
Purchase #7	$73.69	10.753%	$81.6139	$81.61	$81.60	$81.60
7 purchase totals =	$1,001.34		$1,105.5242	$1,105.53	$1,105.55	$1,105.50