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	$201.37	8.197%	$217.8763	$217.88	$217.90	$217.90
Purchase #2	$228.90	13.402%	$259.5772	$259.58	$259.60	$259.60
Purchase #3	$60.59	8.768%	$65.9025	$65.90	$65.90	$65.90
Purchase #4	$237.63	8.125%	$256.9374	$256.94	$256.95	$256.90
Purchase #5	$115.25	12.734%	$129.9259	$129.93	$129.95	$129.90
Purchase #6	$49.25	3.378%	$50.9137	$50.91	$50.90	$50.90
Purchase #7	$32.51	8.842%	$35.3845	$35.38	$35.40	$35.40
7 purchase totals =	$925.50		$1,016.5175	$1,016.52	$1,016.60	$1,016.50