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	$123.31	8.607%	$133.9233	$133.92	$133.90	$133.90
Purchase #2	$189.60	3.566%	$196.3611	$196.36	$196.35	$196.40
Purchase #3	$68.51	5.525%	$72.2952	$72.30	$72.30	$72.30
Purchase #4	$196.58	10.785%	$217.7812	$217.78	$217.80	$217.80
Purchase #5	$48.61	8.140%	$52.5669	$52.57	$52.55	$52.60
Purchase #6	$229.42	11.680%	$256.2163	$256.22	$256.20	$256.20
Purchase #7	$9.47	13.872%	$10.7837	$10.78	$10.80	$10.80
7 purchase totals =	$865.50		$939.9277	$939.93	$939.90	$940.00