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	$197.46	9.130%	$215.4881	$215.49	$215.50	$215.50
Purchase #2	$70.38	13.679%	$80.0073	$80.01	$80.00	$80.00
Purchase #3	$103.80	7.802%	$111.8985	$111.90	$111.90	$111.90
Purchase #4	$61.36	6.841%	$65.5576	$65.56	$65.55	$65.60
Purchase #5	$85.85	6.104%	$91.0903	$91.09	$91.10	$91.10
Purchase #6	$200.72	13.305%	$227.4258	$227.43	$227.45	$227.40
Purchase #7	$162.84	7.734%	$175.434	$175.43	$175.45	$175.40
7 purchase totals =	$882.41		$966.9016	$966.91	$966.95	$966.90