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	$248.91	5.358%	$262.2466	$262.25	$262.25	$262.20
Purchase #2	$102.48	9.766%	$112.4882	$112.49	$112.50	$112.50
Purchase #3	$38.77	7.410%	$41.6429	$41.64	$41.65	$41.60
Purchase #4	$105.67	13.257%	$119.6787	$119.68	$119.70	$119.70
Purchase #5	$90.49	5.218%	$95.2118	$95.21	$95.20	$95.20
Purchase #6	$38.83	4.130%	$40.4337	$40.43	$40.45	$40.40
Purchase #7	$80.73	6.386%	$85.8854	$85.89	$85.90	$85.90
7 purchase totals =	$705.88		$757.5873	$757.59	$757.65	$757.50