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	$214.34	5.144%	$225.3656	$225.37	$225.35	$225.40
Purchase #2	$229.61	8.189%	$248.4128	$248.41	$248.40	$248.40
Purchase #3	$110.46	11.382%	$123.0326	$123.03	$123.05	$123.00
Purchase #4	$81.48	10.342%	$89.9067	$89.91	$89.90	$89.90
Purchase #5	$124.90	12.769%	$140.8485	$140.85	$140.85	$140.80
Purchase #6	$50.35	9.134%	$54.949	$54.95	$54.95	$54.90
Purchase #7	$169.85	4.770%	$177.9518	$177.95	$177.95	$178.00
7 purchase totals =	$980.99		$1,060.4670	$1,060.47	$1,060.45	$1,060.40