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	$112.81	9.524%	$123.554	$123.55	$123.55	$123.60
Purchase #2	$239.90	5.607%	$253.3512	$253.35	$253.35	$253.40
Purchase #3	$75.56	4.447%	$78.9202	$78.92	$78.90	$78.90
Purchase #4	$22.41	9.336%	$24.5022	$24.50	$24.50	$24.50
Purchase #5	$243.44	7.261%	$261.1162	$261.12	$261.10	$261.10
Purchase #6	$66.94	7.669%	$72.0736	$72.07	$72.05	$72.10
Purchase #7	$228.82	3.180%	$236.0965	$236.10	$236.10	$236.10
7 purchase totals =	$989.88		$1,049.6139	$1,049.61	$1,049.55	$1,049.70