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	$59.70	11.759%	$66.7201	$66.72	$66.70	$66.70
Purchase #2	$154.64	8.697%	$168.089	$168.09	$168.10	$168.10
Purchase #3	$68.94	3.229%	$71.1661	$71.17	$71.15	$71.20
Purchase #4	$194.58	6.171%	$206.5875	$206.59	$206.60	$206.60
Purchase #5	$172.67	13.777%	$196.4587	$196.46	$196.45	$196.50
Purchase #6	$175.49	9.582%	$192.3055	$192.31	$192.30	$192.30
Purchase #7	$41.49	11.424%	$46.2298	$46.23	$46.25	$46.20
7 purchase totals =	$867.51		$947.5567	$947.57	$947.55	$947.60