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	$59.99	12.685%	$67.5997	$67.60	$67.60	$67.60
Purchase #2	$171.72	12.139%	$192.5651	$192.57	$192.55	$192.60
Purchase #3	$52.81	9.397%	$57.7726	$57.77	$57.75	$57.80
Purchase #4	$83.36	13.434%	$94.5586	$94.56	$94.55	$94.60
Purchase #5	$182.25	13.493%	$206.841	$206.84	$206.85	$206.80
Purchase #6	$38.82	6.838%	$41.4745	$41.47	$41.45	$41.50
Purchase #7	$41.43	13.115%	$46.8635	$46.86	$46.85	$46.90
7 purchase totals =	$630.38		$707.6750	$707.67	$707.60	$707.80