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	$7.46	5.225%	$7.8498	$7.85	$7.85	$7.80
Purchase #2	$241.69	8.650%	$262.5962	$262.60	$262.60	$262.60
Purchase #3	$79.73	11.675%	$89.0385	$89.04	$89.05	$89.00
Purchase #4	$241.50	8.356%	$261.6797	$261.68	$261.70	$261.70
Purchase #5	$153.89	9.175%	$168.0094	$168.01	$168.00	$168.00
Purchase #6	$171.96	3.491%	$177.9631	$177.96	$177.95	$178.00
Purchase #7	$48.46	5.269%	$51.0134	$51.01	$51.00	$51.00
7 purchase totals =	$944.69		$1,018.1501	$1,018.15	$1,018.15	$1,018.10