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	$248.46	4.494%	$259.6258	$259.63	$259.65	$259.60
Purchase #2	$84.49	12.583%	$95.1214	$95.12	$95.10	$95.10
Purchase #3	$127.59	11.571%	$142.3534	$142.35	$142.35	$142.40
Purchase #4	$240.95	9.432%	$263.6764	$263.68	$263.70	$263.70
Purchase #5	$208.75	3.358%	$215.7598	$215.76	$215.75	$215.80
Purchase #6	$38.98	10.340%	$43.0105	$43.01	$43.00	$43.00
Purchase #7	$107.63	3.729%	$111.6435	$111.64	$111.65	$111.60
7 purchase totals =	$1,056.85		$1,131.1908	$1,131.19	$1,131.20	$1,131.20