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	$106.47	13.718%	$121.0756	$121.08	$121.10	$121.10
Purchase #2	$229.31	9.584%	$251.2871	$251.29	$251.30	$251.30
Purchase #3	$174.79	12.665%	$196.9272	$196.93	$196.95	$196.90
Purchase #4	$188.26	10.736%	$208.4716	$208.47	$208.45	$208.50
Purchase #5	$234.83	13.787%	$267.206	$267.21	$267.20	$267.20
Purchase #6	$119.57	9.680%	$131.1444	$131.14	$131.15	$131.10
Purchase #7	$82.59	5.208%	$86.8913	$86.89	$86.90	$86.90
7 purchase totals =	$1,135.82		$1,263.0032	$1,263.01	$1,263.05	$1,263.00