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	$217.36	10.626%	$240.4567	$240.46	$240.45	$240.50
Purchase #2	$124.42	5.682%	$131.4895	$131.49	$131.50	$131.50
Purchase #3	$59.76	3.587%	$61.9036	$61.90	$61.90	$61.90
Purchase #4	$100.35	3.391%	$103.7529	$103.75	$103.75	$103.80
Purchase #5	$113.40	7.248%	$121.6192	$121.62	$121.60	$121.60
Purchase #6	$165.77	10.402%	$183.0134	$183.01	$183.00	$183.00
Purchase #7	$229.73	11.767%	$256.7623	$256.76	$256.75	$256.80
7 purchase totals =	$1,010.79		$1,098.9976	$1,098.99	$1,098.95	$1,099.10