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	$195.98	11.302%	$218.1297	$218.13	$218.15	$218.10
Purchase #2	$105.51	4.139%	$109.8771	$109.88	$109.90	$109.90
Purchase #3	$116.47	5.576%	$122.9644	$122.96	$122.95	$123.00
Purchase #4	$139.37	9.310%	$152.3453	$152.35	$152.35	$152.30
Purchase #5	$135.62	3.208%	$139.9707	$139.97	$139.95	$140.00
Purchase #6	$125.47	10.321%	$138.4198	$138.42	$138.40	$138.40
Purchase #7	$157.50	7.241%	$168.9046	$168.90	$168.90	$168.90
7 purchase totals =	$975.92		$1,050.6116	$1,050.61	$1,050.60	$1,050.60