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	$207.38	8.422%	$224.8455	$224.85	$224.85	$224.80
Purchase #2	$228.90	5.200%	$240.8028	$240.80	$240.80	$240.80
Purchase #3	$150.54	8.798%	$163.7845	$163.78	$163.80	$163.80
Purchase #4	$201.99	7.693%	$217.5291	$217.53	$217.55	$217.50
Purchase #5	$42.83	6.516%	$45.6208	$45.62	$45.60	$45.60
Purchase #6	$53.34	3.847%	$55.392	$55.39	$55.40	$55.40
Purchase #7	$136.40	11.795%	$152.4884	$152.49	$152.50	$152.50
7 purchase totals =	$1,021.38		$1,100.4631	$1,100.46	$1,100.50	$1,100.40