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	$72.95	7.477%	$78.4045	$78.40	$78.40	$78.40
Purchase #2	$245.58	5.412%	$258.8708	$258.87	$258.85	$258.90
Purchase #3	$11.67	8.189%	$12.6257	$12.63	$12.65	$12.60
Purchase #4	$130.26	11.762%	$145.5812	$145.58	$145.60	$145.60
Purchase #5	$33.41	11.124%	$37.1265	$37.13	$37.15	$37.10
Purchase #6	$118.83	10.648%	$131.483	$131.48	$131.50	$131.50
Purchase #7	$212.63	6.509%	$226.4701	$226.47	$226.45	$226.50
7 purchase totals =	$825.33		$890.5618	$890.56	$890.60	$890.60