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	$108.94	3.645%	$112.9109	$112.91	$112.90	$112.90
Purchase #2	$104.68	6.661%	$111.6527	$111.65	$111.65	$111.70
Purchase #3	$30.70	6.239%	$32.6154	$32.62	$32.60	$32.60
Purchase #4	$65.80	8.689%	$71.5174	$71.52	$71.50	$71.50
Purchase #5	$52.87	13.256%	$59.8784	$59.88	$59.90	$59.90
Purchase #6	$156.69	12.725%	$176.6288	$176.63	$176.65	$176.60
Purchase #7	$108.85	12.532%	$122.4911	$122.49	$122.50	$122.50
7 purchase totals =	$628.53		$687.6947	$687.70	$687.70	$687.70