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	$216.35	11.786%	$241.849	$241.85	$241.85	$241.80
Purchase #2	$33.65	6.754%	$35.9227	$35.92	$35.90	$35.90
Purchase #3	$36.89	4.469%	$38.5386	$38.54	$38.55	$38.50
Purchase #4	$214.51	13.122%	$242.658	$242.66	$242.65	$242.70
Purchase #5	$168.25	7.839%	$181.4391	$181.44	$181.45	$181.40
Purchase #6	$9.78	11.756%	$10.9297	$10.93	$10.95	$10.90
Purchase #7	$242.87	6.616%	$258.9383	$258.94	$258.95	$258.90
7 purchase totals =	$922.30		$1,010.2754	$1,010.28	$1,010.30	$1,010.10