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	$119.39	7.811%	$128.7156	$128.72	$128.70	$128.70
Purchase #2	$137.29	8.115%	$148.4311	$148.43	$148.45	$148.40
Purchase #3	$80.30	10.367%	$88.6247	$88.62	$88.60	$88.60
Purchase #4	$75.64	10.389%	$83.4982	$83.50	$83.50	$83.50
Purchase #5	$114.98	11.856%	$128.612	$128.61	$128.60	$128.60
Purchase #6	$163.73	3.420%	$169.3296	$169.33	$169.35	$169.30
Purchase #7	$181.30	6.621%	$193.3039	$193.30	$193.30	$193.30
7 purchase totals =	$872.63		$940.5151	$940.51	$940.50	$940.40