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	$227.50	4.216%	$237.0914	$237.09	$237.10	$237.10
Purchase #2	$6.98	13.208%	$7.9019	$7.90	$7.90	$7.90
Purchase #3	$86.78	9.848%	$95.3261	$95.33	$95.35	$95.30
Purchase #4	$37.99	3.232%	$39.2178	$39.22	$39.20	$39.20
Purchase #5	$87.51	3.732%	$90.7759	$90.78	$90.80	$90.80
Purchase #6	$94.67	10.807%	$104.901	$104.90	$104.90	$104.90
Purchase #7	$31.42	12.789%	$35.4383	$35.44	$35.45	$35.40
7 purchase totals =	$572.85		$610.6524	$610.66	$610.70	$610.60