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	$225.81	9.304%	$246.8194	$246.82	$246.80	$246.80
Purchase #2	$47.94	7.367%	$51.4717	$51.47	$51.45	$51.50
Purchase #3	$81.30	11.294%	$90.482	$90.48	$90.50	$90.50
Purchase #4	$159.67	3.772%	$165.6928	$165.69	$165.70	$165.70
Purchase #5	$140.28	13.522%	$159.2487	$159.25	$159.25	$159.20
Purchase #6	$38.98	10.405%	$43.0359	$43.04	$43.05	$43.00
Purchase #7	$187.87	4.801%	$196.8896	$196.89	$196.90	$196.90
7 purchase totals =	$881.85		$953.6401	$953.64	$953.65	$953.60