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	$108.32	7.217%	$116.1375	$116.14	$116.15	$116.10
Purchase #2	$225.96	6.270%	$240.1277	$240.13	$240.15	$240.10
Purchase #3	$10.34	5.691%	$10.9284	$10.93	$10.95	$10.90
Purchase #4	$242.69	4.712%	$254.1256	$254.13	$254.15	$254.10
Purchase #5	$163.75	13.848%	$186.4261	$186.43	$186.45	$186.40
Purchase #6	$155.84	5.730%	$164.7696	$164.77	$164.75	$164.80
Purchase #7	$112.98	13.637%	$128.3871	$128.39	$128.40	$128.40
7 purchase totals =	$1,019.88		$1,100.9020	$1,100.92	$1,101.00	$1,100.80