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	$196.81	10.535%	$217.5439	$217.54	$217.55	$217.50
Purchase #2	$87.96	4.853%	$92.2287	$92.23	$92.25	$92.20
Purchase #3	$206.57	10.572%	$228.4086	$228.41	$228.40	$228.40
Purchase #4	$201.85	5.762%	$213.4806	$213.48	$213.50	$213.50
Purchase #5	$55.53	6.782%	$59.296	$59.30	$59.30	$59.30
Purchase #6	$38.94	12.717%	$43.892	$43.89	$43.90	$43.90
Purchase #7	$163.60	5.504%	$172.6045	$172.60	$172.60	$172.60
7 purchase totals =	$951.26		$1,027.4543	$1,027.45	$1,027.50	$1,027.40