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	$168.26	9.747%	$184.6603	$184.66	$184.65	$184.70
Purchase #2	$144.81	9.488%	$158.5496	$158.55	$158.55	$158.50
Purchase #3	$92.53	7.519%	$99.4873	$99.49	$99.50	$99.50
Purchase #4	$119.95	9.462%	$131.2997	$131.30	$131.30	$131.30
Purchase #5	$202.79	9.619%	$222.2964	$222.30	$222.30	$222.30
Purchase #6	$107.28	12.410%	$120.5934	$120.59	$120.60	$120.60
Purchase #7	$39.75	13.709%	$45.1993	$45.20	$45.20	$45.20
7 purchase totals =	$875.37		$962.0860	$962.09	$962.10	$962.10