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	$192.42	3.627%	$199.3991	$199.40	$199.40	$199.40
Purchase #2	$166.78	12.390%	$187.444	$187.44	$187.45	$187.40
Purchase #3	$60.33	8.300%	$65.3374	$65.34	$65.35	$65.30
Purchase #4	$168.69	6.266%	$179.2601	$179.26	$179.25	$179.30
Purchase #5	$139.30	3.627%	$144.3524	$144.35	$144.35	$144.40
Purchase #6	$144.75	5.617%	$152.8806	$152.88	$152.90	$152.90
Purchase #7	$41.68	13.362%	$47.2493	$47.25	$47.25	$47.20
7 purchase totals =	$913.95		$975.9229	$975.92	$975.95	$975.90