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	$33.46	5.309%	$35.2364	$35.24	$35.25	$35.20
Purchase #2	$26.36	8.575%	$28.6204	$28.62	$28.60	$28.60
Purchase #3	$233.25	3.702%	$241.8849	$241.88	$241.90	$241.90
Purchase #4	$191.58	13.360%	$217.1751	$217.18	$217.20	$217.20
Purchase #5	$166.57	3.484%	$172.3733	$172.37	$172.35	$172.40
Purchase #6	$166.83	7.872%	$179.9629	$179.96	$179.95	$180.00
Purchase #7	$156.51	7.795%	$168.71	$168.71	$168.70	$168.70
7 purchase totals =	$974.56		$1,043.9630	$1,043.96	$1,043.95	$1,044.00