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	$205.42	13.358%	$232.86	$232.86	$232.85	$232.90
Purchase #2	$51.30	11.669%	$57.2862	$57.29	$57.30	$57.30
Purchase #3	$210.70	5.563%	$222.4212	$222.42	$222.40	$222.40
Purchase #4	$136.88	3.268%	$141.3532	$141.35	$141.35	$141.40
Purchase #5	$6.79	7.336%	$7.2881	$7.29	$7.30	$7.30
Purchase #6	$138.39	10.124%	$152.4006	$152.40	$152.40	$152.40
Purchase #7	$175.65	11.680%	$196.1659	$196.17	$196.15	$196.20
7 purchase totals =	$925.13		$1,009.7752	$1,009.78	$1,009.75	$1,009.90