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	$54.54	13.156%	$61.7153	$61.72	$61.70	$61.70
Purchase #2	$77.47	7.700%	$83.4352	$83.44	$83.45	$83.40
Purchase #3	$112.49	4.499%	$117.5509	$117.55	$117.55	$117.60
Purchase #4	$166.46	13.259%	$188.5309	$188.53	$188.55	$188.50
Purchase #5	$222.81	12.394%	$250.4251	$250.43	$250.45	$250.40
Purchase #6	$169.48	12.624%	$190.8752	$190.88	$190.90	$190.90
Purchase #7	$123.47	7.619%	$132.8772	$132.88	$132.90	$132.90
7 purchase totals =	$926.72		$1,025.4098	$1,025.43	$1,025.50	$1,025.40