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	$116.96	12.296%	$131.3414	$131.34	$131.35	$131.30
Purchase #2	$93.39	11.143%	$103.7964	$103.80	$103.80	$103.80
Purchase #3	$221.72	12.703%	$249.8851	$249.89	$249.90	$249.90
Purchase #4	$22.38	9.546%	$24.5164	$24.52	$24.50	$24.50
Purchase #5	$236.31	4.475%	$246.8849	$246.88	$246.90	$246.90
Purchase #6	$88.29	9.227%	$96.4365	$96.44	$96.45	$96.40
Purchase #7	$159.80	7.650%	$172.0247	$172.02	$172.00	$172.00
7 purchase totals =	$938.85		$1,024.8854	$1,024.89	$1,024.90	$1,024.80