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	$195.96	6.611%	$208.9149	$208.91	$208.90	$208.90
Purchase #2	$171.49	4.158%	$178.6206	$178.62	$178.60	$178.60
Purchase #3	$153.79	9.210%	$167.9541	$167.95	$167.95	$168.00
Purchase #4	$62.79	4.545%	$65.6438	$65.64	$65.65	$65.60
Purchase #5	$38.46	4.829%	$40.3172	$40.32	$40.30	$40.30
Purchase #6	$155.71	5.764%	$164.6851	$164.69	$164.70	$164.70
Purchase #7	$137.42	13.613%	$156.127	$156.13	$156.15	$156.10
7 purchase totals =	$915.62		$982.2627	$982.26	$982.25	$982.20