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	$104.39	7.870%	$112.6055	$112.61	$112.60	$112.60
Purchase #2	$53.54	5.151%	$56.2978	$56.30	$56.30	$56.30
Purchase #3	$66.91	3.508%	$69.2572	$69.26	$69.25	$69.30
Purchase #4	$158.48	12.617%	$178.4754	$178.48	$178.50	$178.50
Purchase #5	$59.96	13.630%	$68.1325	$68.13	$68.15	$68.10
Purchase #6	$143.31	6.379%	$152.4517	$152.45	$152.45	$152.50
Purchase #7	$55.26	4.842%	$57.9357	$57.94	$57.95	$57.90
7 purchase totals =	$641.85		$695.1558	$695.17	$695.20	$695.20