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	$249.99	10.507%	$276.2564	$276.26	$276.25	$276.30
Purchase #2	$115.39	5.143%	$121.3245	$121.32	$121.30	$121.30
Purchase #3	$173.31	3.300%	$179.0292	$179.03	$179.05	$179.00
Purchase #4	$190.33	4.737%	$199.3459	$199.35	$199.35	$199.30
Purchase #5	$70.89	13.647%	$80.5644	$80.56	$80.55	$80.60
Purchase #6	$205.96	7.728%	$221.8766	$221.88	$221.90	$221.90
Purchase #7	$24.84	10.440%	$27.4333	$27.43	$27.45	$27.40
7 purchase totals =	$1,030.71		$1,105.8303	$1,105.83	$1,105.85	$1,105.80