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	$104.58	12.383%	$117.5301	$117.53	$117.55	$117.50
Purchase #2	$57.76	3.666%	$59.8775	$59.88	$59.90	$59.90
Purchase #3	$52.80	5.143%	$55.5155	$55.52	$55.50	$55.50
Purchase #4	$111.92	8.291%	$121.1993	$121.20	$121.20	$121.20
Purchase #5	$226.97	12.578%	$255.5183	$255.52	$255.50	$255.50
Purchase #6	$200.60	10.467%	$221.5968	$221.60	$221.60	$221.60
Purchase #7	$167.38	5.846%	$177.165	$177.17	$177.15	$177.20
7 purchase totals =	$922.01		$1,008.4025	$1,008.42	$1,008.40	$1,008.40