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	$206.38	13.595%	$234.4374	$234.44	$234.45	$234.40
Purchase #2	$9.76	10.667%	$10.8011	$10.80	$10.80	$10.80
Purchase #3	$65.56	11.598%	$73.1636	$73.16	$73.15	$73.20
Purchase #4	$99.27	12.678%	$111.8555	$111.86	$111.85	$111.90
Purchase #5	$208.53	4.338%	$217.576	$217.58	$217.60	$217.60
Purchase #6	$147.88	11.467%	$164.8374	$164.84	$164.85	$164.80
Purchase #7	$105.49	11.318%	$117.4294	$117.43	$117.45	$117.40
7 purchase totals =	$842.87		$930.1004	$930.11	$930.15	$930.10