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	$81.46	4.757%	$85.3351	$85.34	$85.35	$85.30
Purchase #2	$198.34	12.302%	$222.7398	$222.74	$222.75	$222.70
Purchase #3	$226.25	10.216%	$249.3637	$249.36	$249.35	$249.40
Purchase #4	$43.82	9.131%	$47.8212	$47.82	$47.80	$47.80
Purchase #5	$154.98	4.452%	$161.8797	$161.88	$161.90	$161.90
Purchase #6	$148.47	6.488%	$158.1027	$158.10	$158.10	$158.10
Purchase #7	$29.72	5.592%	$31.3819	$31.38	$31.40	$31.40
7 purchase totals =	$883.04		$956.6241	$956.62	$956.65	$956.60