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	$145.37	7.689%	$156.5475	$156.55	$156.55	$156.50
Purchase #2	$152.69	6.381%	$162.4331	$162.43	$162.45	$162.40
Purchase #3	$31.71	7.105%	$33.963	$33.96	$33.95	$34.00
Purchase #4	$183.59	3.310%	$189.6668	$189.67	$189.65	$189.70
Purchase #5	$161.55	12.387%	$181.5612	$181.56	$181.55	$181.60
Purchase #6	$205.90	8.204%	$222.792	$222.79	$222.80	$222.80
Purchase #7	$122.64	7.390%	$131.7031	$131.70	$131.70	$131.70
7 purchase totals =	$1,003.45		$1,078.6667	$1,078.66	$1,078.65	$1,078.70