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	$234.40	11.725%	$261.8834	$261.88	$261.90	$261.90
Purchase #2	$83.39	10.183%	$91.8816	$91.88	$91.90	$91.90
Purchase #3	$103.26	8.226%	$111.7542	$111.75	$111.75	$111.80
Purchase #4	$229.81	13.456%	$260.7332	$260.73	$260.75	$260.70
Purchase #5	$36.38	12.548%	$40.945	$40.95	$40.95	$40.90
Purchase #6	$67.64	12.746%	$76.2614	$76.26	$76.25	$76.30
Purchase #7	$190.40	4.365%	$198.711	$198.71	$198.70	$198.70
7 purchase totals =	$945.28		$1,042.1698	$1,042.16	$1,042.20	$1,042.20