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	$126.80	8.671%	$137.7948	$137.79	$137.80	$137.80
Purchase #2	$102.56	8.610%	$111.3904	$111.39	$111.40	$111.40
Purchase #3	$55.87	7.265%	$59.929	$59.93	$59.95	$59.90
Purchase #4	$35.46	8.743%	$38.5603	$38.56	$38.55	$38.60
Purchase #5	$183.58	11.646%	$204.9597	$204.96	$204.95	$205.00
Purchase #6	$239.66	11.612%	$267.4893	$267.49	$267.50	$267.50
Purchase #7	$107.84	10.825%	$119.5137	$119.51	$119.50	$119.50
7 purchase totals =	$851.77		$939.6372	$939.63	$939.65	$939.70