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	$194.96	13.244%	$220.7805	$220.78	$220.80	$220.80
Purchase #2	$172.82	7.759%	$186.2291	$186.23	$186.25	$186.20
Purchase #3	$71.99	8.855%	$78.3647	$78.36	$78.35	$78.40
Purchase #4	$110.49	9.137%	$120.5855	$120.59	$120.60	$120.60
Purchase #5	$163.71	5.569%	$172.827	$172.83	$172.85	$172.80
Purchase #6	$174.86	3.760%	$181.4347	$181.43	$181.45	$181.40
Purchase #7	$163.58	11.386%	$182.2052	$182.21	$182.20	$182.20
7 purchase totals =	$1,052.41		$1,142.4267	$1,142.43	$1,142.50	$1,142.40