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	$132.63	8.112%	$143.3889	$143.39	$143.40	$143.40
Purchase #2	$179.85	6.774%	$192.033	$192.03	$192.05	$192.00
Purchase #3	$124.62	7.386%	$133.8244	$133.82	$133.80	$133.80
Purchase #4	$142.72	13.837%	$162.4682	$162.47	$162.45	$162.50
Purchase #5	$68.49	4.550%	$71.6063	$71.61	$71.60	$71.60
Purchase #6	$84.97	12.426%	$95.5284	$95.53	$95.55	$95.50
Purchase #7	$212.58	4.588%	$222.3332	$222.33	$222.35	$222.30
7 purchase totals =	$945.86		$1,021.1824	$1,021.18	$1,021.20	$1,021.10