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	$79.64	7.858%	$85.8981	$85.90	$85.90	$85.90
Purchase #2	$246.68	13.680%	$280.4258	$280.43	$280.45	$280.40
Purchase #3	$199.75	8.625%	$216.9784	$216.98	$217.00	$217.00
Purchase #4	$54.90	8.810%	$59.7367	$59.74	$59.75	$59.70
Purchase #5	$25.57	9.240%	$27.9327	$27.93	$27.95	$27.90
Purchase #6	$144.40	9.254%	$157.7628	$157.76	$157.75	$157.80
Purchase #7	$132.59	6.771%	$141.5677	$141.57	$141.55	$141.60
7 purchase totals =	$883.53		$970.3022	$970.31	$970.35	$970.30