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	$171.65	11.545%	$191.467	$191.47	$191.45	$191.50
Purchase #2	$63.95	5.189%	$67.2684	$67.27	$67.25	$67.30
Purchase #3	$29.32	7.203%	$31.4319	$31.43	$31.45	$31.40
Purchase #4	$69.91	9.506%	$76.5556	$76.56	$76.55	$76.60
Purchase #5	$196.56	9.723%	$215.6715	$215.67	$215.65	$215.70
Purchase #6	$68.55	12.126%	$76.8624	$76.86	$76.85	$76.90
Purchase #7	$158.27	10.868%	$175.4708	$175.47	$175.45	$175.50
7 purchase totals =	$758.21		$834.7276	$834.73	$834.65	$834.90