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	$247.25	13.852%	$281.4991	$281.50	$281.50	$281.50
Purchase #2	$94.53	6.752%	$100.9127	$100.91	$100.90	$100.90
Purchase #3	$126.64	12.748%	$142.7841	$142.78	$142.80	$142.80
Purchase #4	$110.87	13.487%	$125.823	$125.82	$125.80	$125.80
Purchase #5	$94.33	10.509%	$104.2431	$104.24	$104.25	$104.20
Purchase #6	$44.59	12.250%	$50.0523	$50.05	$50.05	$50.10
Purchase #7	$71.32	12.787%	$80.4397	$80.44	$80.45	$80.40
7 purchase totals =	$789.53		$885.7540	$885.74	$885.75	$885.70