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	$114.49	8.165%	$123.8381	$123.84	$123.85	$123.80
Purchase #2	$19.86	4.346%	$20.7231	$20.72	$20.70	$20.70
Purchase #3	$151.90	11.828%	$169.8667	$169.87	$169.85	$169.90
Purchase #4	$76.38	10.510%	$84.4075	$84.41	$84.40	$84.40
Purchase #5	$239.69	6.587%	$255.4784	$255.48	$255.50	$255.50
Purchase #6	$73.83	7.808%	$79.5946	$79.59	$79.60	$79.60
Purchase #7	$77.74	6.153%	$82.5233	$82.52	$82.50	$82.50
7 purchase totals =	$753.89		$816.4317	$816.43	$816.40	$816.40