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	$40.60	7.151%	$43.5033	$43.50	$43.50	$43.50
Purchase #2	$183.54	13.807%	$208.8814	$208.88	$208.90	$208.90
Purchase #3	$109.94	10.688%	$121.6904	$121.69	$121.70	$121.70
Purchase #4	$231.39	5.243%	$243.5218	$243.52	$243.50	$243.50
Purchase #5	$68.96	13.601%	$78.3392	$78.34	$78.35	$78.30
Purchase #6	$162.82	7.309%	$174.7205	$174.72	$174.70	$174.70
Purchase #7	$140.99	8.196%	$152.5455	$152.55	$152.55	$152.50
7 purchase totals =	$938.24		$1,023.2021	$1,023.20	$1,023.20	$1,023.10