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	$159.65	3.243%	$164.8274	$164.83	$164.85	$164.80
Purchase #2	$130.74	7.493%	$140.5363	$140.54	$140.55	$140.50
Purchase #3	$118.29	10.815%	$131.0831	$131.08	$131.10	$131.10
Purchase #4	$10.59	3.265%	$10.9358	$10.94	$10.95	$10.90
Purchase #5	$140.90	13.148%	$159.4255	$159.43	$159.45	$159.40
Purchase #6	$218.57	12.663%	$246.2475	$246.25	$246.25	$246.20
Purchase #7	$139.65	10.850%	$154.802	$154.80	$154.80	$154.80
7 purchase totals =	$918.39		$1,007.8576	$1,007.87	$1,007.95	$1,007.70