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	$102.60	10.845%	$113.727	$113.73	$113.75	$113.70
Purchase #2	$112.91	3.226%	$116.5525	$116.55	$116.55	$116.60
Purchase #3	$51.91	6.333%	$55.1975	$55.20	$55.20	$55.20
Purchase #4	$87.29	9.154%	$95.2805	$95.28	$95.30	$95.30
Purchase #5	$82.96	9.573%	$90.9018	$90.90	$90.90	$90.90
Purchase #6	$140.43	3.667%	$145.5796	$145.58	$145.60	$145.60
Purchase #7	$144.56	5.617%	$152.6799	$152.68	$152.70	$152.70
7 purchase totals =	$722.66		$769.9188	$769.92	$770.00	$770.00