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	$35.53	13.748%	$40.4147	$40.41	$40.40	$40.40
Purchase #2	$244.60	11.579%	$272.9222	$272.92	$272.90	$272.90
Purchase #3	$43.40	6.392%	$46.1741	$46.17	$46.15	$46.20
Purchase #4	$219.41	5.484%	$231.4424	$231.44	$231.45	$231.40
Purchase #5	$238.59	4.131%	$248.4462	$248.45	$248.45	$248.40
Purchase #6	$243.27	4.208%	$253.5068	$253.51	$253.50	$253.50
Purchase #7	$37.43	13.327%	$42.4183	$42.42	$42.40	$42.40
7 purchase totals =	$1,062.23		$1,135.3247	$1,135.32	$1,135.25	$1,135.20