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	$16.37	5.417%	$17.2568	$17.26	$17.25	$17.30
Purchase #2	$36.71	4.445%	$38.3418	$38.34	$38.35	$38.30
Purchase #3	$59.84	6.477%	$63.7158	$63.72	$63.70	$63.70
Purchase #4	$161.33	10.192%	$177.7728	$177.77	$177.75	$177.80
Purchase #5	$78.30	3.339%	$80.9144	$80.91	$80.90	$80.90
Purchase #6	$183.38	7.371%	$196.8969	$196.90	$196.90	$196.90
Purchase #7	$109.37	13.305%	$123.9217	$123.92	$123.90	$123.90
7 purchase totals =	$645.30		$698.8202	$698.82	$698.75	$698.80