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	$216.47	13.701%	$246.1286	$246.13	$246.15	$246.10
Purchase #2	$80.42	8.235%	$87.0426	$87.04	$87.05	$87.00
Purchase #3	$188.98	3.379%	$195.3656	$195.37	$195.35	$195.40
Purchase #4	$245.46	11.393%	$273.4253	$273.43	$273.45	$273.40
Purchase #5	$141.65	9.443%	$155.026	$155.03	$155.05	$155.00
Purchase #6	$93.94	10.198%	$103.52	$103.52	$103.50	$103.50
Purchase #7	$179.43	9.503%	$196.4812	$196.48	$196.50	$196.50
7 purchase totals =	$1,146.35		$1,256.9893	$1,257.00	$1,257.05	$1,256.90