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	$117.87	11.532%	$131.4628	$131.46	$131.45	$131.50
Purchase #2	$240.81	13.342%	$272.9389	$272.94	$272.95	$272.90
Purchase #3	$91.30	6.736%	$97.45	$97.45	$97.45	$97.50
Purchase #4	$247.72	5.291%	$260.8269	$260.83	$260.85	$260.80
Purchase #5	$124.83	5.116%	$131.2163	$131.22	$131.20	$131.20
Purchase #6	$232.29	3.873%	$241.2866	$241.29	$241.30	$241.30
Purchase #7	$42.71	11.604%	$47.6661	$47.67	$47.65	$47.70
7 purchase totals =	$1,097.53		$1,182.8476	$1,182.86	$1,182.85	$1,182.90