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	$156.45	5.109%	$164.443	$164.44	$164.45	$164.40
Purchase #2	$35.80	4.308%	$37.3423	$37.34	$37.35	$37.30
Purchase #3	$244.77	5.785%	$258.9299	$258.93	$258.95	$258.90
Purchase #4	$202.25	11.438%	$225.3834	$225.38	$225.40	$225.40
Purchase #5	$80.81	3.677%	$83.7814	$83.78	$83.80	$83.80
Purchase #6	$130.73	8.444%	$141.7688	$141.77	$141.75	$141.80
Purchase #7	$154.42	9.757%	$169.4868	$169.49	$169.50	$169.50
7 purchase totals =	$1,005.23		$1,081.1356	$1,081.13	$1,081.20	$1,081.10