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	$189.79	3.579%	$196.5826	$196.58	$196.60	$196.60
Purchase #2	$87.81	7.666%	$94.5415	$94.54	$94.55	$94.50
Purchase #3	$180.28	5.332%	$189.8925	$189.89	$189.90	$189.90
Purchase #4	$49.41	7.739%	$53.2338	$53.23	$53.25	$53.20
Purchase #5	$219.75	9.763%	$241.2042	$241.20	$241.20	$241.20
Purchase #6	$174.40	10.539%	$192.78	$192.78	$192.80	$192.80
Purchase #7	$63.36	6.291%	$67.346	$67.35	$67.35	$67.30
7 purchase totals =	$964.80		$1,035.5806	$1,035.57	$1,035.65	$1,035.50