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	$78.32	13.870%	$89.183	$89.18	$89.20	$89.20
Purchase #2	$51.87	11.324%	$57.7438	$57.74	$57.75	$57.70
Purchase #3	$97.93	13.812%	$111.4561	$111.46	$111.45	$111.50
Purchase #4	$72.83	7.763%	$78.4838	$78.48	$78.50	$78.50
Purchase #5	$190.97	12.850%	$215.5096	$215.51	$215.50	$215.50
Purchase #6	$247.34	7.337%	$265.4873	$265.49	$265.50	$265.50
Purchase #7	$7.77	13.874%	$8.848	$8.85	$8.85	$8.80
7 purchase totals =	$747.03		$826.7116	$826.71	$826.75	$826.70