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	$212.75	12.437%	$239.2097	$239.21	$239.20	$239.20
Purchase #2	$71.63	10.144%	$78.8961	$78.90	$78.90	$78.90
Purchase #3	$69.89	12.367%	$78.5333	$78.53	$78.55	$78.50
Purchase #4	$231.97	12.794%	$261.6482	$261.65	$261.65	$261.60
Purchase #5	$72.98	7.692%	$78.5936	$78.59	$78.60	$78.60
Purchase #6	$206.81	7.792%	$222.9246	$222.92	$222.90	$222.90
Purchase #7	$92.97	13.841%	$105.838	$105.84	$105.85	$105.80
7 purchase totals =	$959.00		$1,065.6435	$1,065.64	$1,065.65	$1,065.50