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	$131.94	8.578%	$143.2578	$143.26	$143.25	$143.30
Purchase #2	$98.97	13.874%	$112.7011	$112.70	$112.70	$112.70
Purchase #3	$94.89	3.400%	$98.1163	$98.12	$98.10	$98.10
Purchase #4	$122.82	4.705%	$128.5987	$128.60	$128.60	$128.60
Purchase #5	$38.84	9.629%	$42.5799	$42.58	$42.60	$42.60
Purchase #6	$55.29	8.279%	$59.8675	$59.87	$59.85	$59.90
Purchase #7	$112.74	3.659%	$116.8652	$116.87	$116.85	$116.90
7 purchase totals =	$655.49		$701.9865	$702.00	$701.95	$702.10