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	$210.65	13.334%	$238.7381	$238.74	$238.75	$238.70
Purchase #2	$115.79	13.344%	$131.241	$131.24	$131.25	$131.20
Purchase #3	$208.40	3.105%	$214.8708	$214.87	$214.85	$214.90
Purchase #4	$90.60	4.789%	$94.9388	$94.94	$94.95	$94.90
Purchase #5	$37.38	10.461%	$41.2903	$41.29	$41.30	$41.30
Purchase #6	$233.35	7.354%	$250.5106	$250.51	$250.50	$250.50
Purchase #7	$38.94	9.862%	$42.7803	$42.78	$42.80	$42.80
7 purchase totals =	$935.11		$1,014.3699	$1,014.37	$1,014.40	$1,014.30