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	$54.84	13.350%	$62.1611	$62.16	$62.15	$62.20
Purchase #2	$75.38	10.683%	$83.4328	$83.43	$83.45	$83.40
Purchase #3	$103.29	5.874%	$109.3573	$109.36	$109.35	$109.40
Purchase #4	$6.80	13.240%	$7.7003	$7.70	$7.70	$7.70
Purchase #5	$247.57	13.708%	$281.5069	$281.51	$281.50	$281.50
Purchase #6	$44.80	3.695%	$46.4554	$46.46	$46.45	$46.50
Purchase #7	$33.59	10.775%	$37.2093	$37.21	$37.20	$37.20
7 purchase totals =	$566.27		$627.8231	$627.83	$627.80	$627.90