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	$203.81	11.580%	$227.4112	$227.41	$227.40	$227.40
Purchase #2	$13.88	4.161%	$14.4575	$14.46	$14.45	$14.50
Purchase #3	$145.83	3.141%	$150.4105	$150.41	$150.40	$150.40
Purchase #4	$245.49	7.164%	$263.0769	$263.08	$263.10	$263.10
Purchase #5	$142.56	13.669%	$162.0465	$162.05	$162.05	$162.00
Purchase #6	$59.72	13.537%	$67.8043	$67.80	$67.80	$67.80
Purchase #7	$77.73	10.662%	$86.0176	$86.02	$86.00	$86.00
7 purchase totals =	$889.02		$971.2245	$971.23	$971.20	$971.20