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	$54.79	5.163%	$57.6188	$57.62	$57.60	$57.60
Purchase #2	$78.68	9.312%	$86.0067	$86.01	$86.00	$86.00
Purchase #3	$74.46	5.476%	$78.5374	$78.54	$78.55	$78.50
Purchase #4	$218.96	11.397%	$243.9149	$243.91	$243.90	$243.90
Purchase #5	$187.71	13.566%	$213.1747	$213.17	$213.15	$213.20
Purchase #6	$215.65	11.832%	$241.1657	$241.17	$241.15	$241.20
Purchase #7	$204.69	12.652%	$230.5874	$230.59	$230.60	$230.60
7 purchase totals =	$1,034.94		$1,151.0056	$1,151.01	$1,150.95	$1,151.00