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	$102.93	9.225%	$112.4253	$112.43	$112.45	$112.40
Purchase #2	$249.72	9.705%	$273.9553	$273.96	$273.95	$274.00
Purchase #3	$226.47	4.521%	$236.7087	$236.71	$236.70	$236.70
Purchase #4	$130.27	4.869%	$136.6128	$136.61	$136.60	$136.60
Purchase #5	$34.40	7.751%	$37.0663	$37.07	$37.05	$37.10
Purchase #6	$75.78	3.783%	$78.6468	$78.65	$78.65	$78.60
Purchase #7	$179.34	7.161%	$192.1825	$192.18	$192.20	$192.20
7 purchase totals =	$998.91		$1,067.5977	$1,067.61	$1,067.60	$1,067.60