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	$248.44	4.184%	$258.8347	$258.83	$258.85	$258.80
Purchase #2	$82.50	12.675%	$92.9569	$92.96	$92.95	$93.00
Purchase #3	$91.69	9.482%	$100.384	$100.38	$100.40	$100.40
Purchase #4	$188.30	10.716%	$208.4782	$208.48	$208.50	$208.50
Purchase #5	$116.97	4.195%	$121.8769	$121.88	$121.90	$121.90
Purchase #6	$239.83	5.850%	$253.8601	$253.86	$253.85	$253.90
Purchase #7	$84.31	7.312%	$90.4747	$90.47	$90.45	$90.50
7 purchase totals =	$1,052.04		$1,126.8655	$1,126.86	$1,126.90	$1,127.00