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	$151.33	8.742%	$164.5593	$164.56	$164.55	$164.60
Purchase #2	$162.73	7.232%	$174.4986	$174.50	$174.50	$174.50
Purchase #3	$200.74	3.638%	$208.0429	$208.04	$208.05	$208.00
Purchase #4	$63.85	12.131%	$71.5956	$71.60	$71.60	$71.60
Purchase #5	$194.69	11.358%	$216.8029	$216.80	$216.80	$216.80
Purchase #6	$199.81	9.542%	$218.8759	$218.88	$218.90	$218.90
Purchase #7	$113.29	12.810%	$127.8024	$127.80	$127.80	$127.80
7 purchase totals =	$1,086.44		$1,182.1776	$1,182.18	$1,182.20	$1,182.20