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	$12.54	12.687%	$14.1309	$14.13	$14.15	$14.10
Purchase #2	$21.38	3.595%	$22.1486	$22.15	$22.15	$22.10
Purchase #3	$216.71	6.689%	$231.2057	$231.21	$231.20	$231.20
Purchase #4	$247.34	13.520%	$280.7804	$280.78	$280.80	$280.80
Purchase #5	$123.30	5.651%	$130.2677	$130.27	$130.25	$130.30
Purchase #6	$63.48	4.795%	$66.5239	$66.52	$66.50	$66.50
Purchase #7	$73.52	7.109%	$78.7465	$78.75	$78.75	$78.70
7 purchase totals =	$758.27		$823.8037	$823.81	$823.80	$823.70