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	$179.39	13.606%	$203.7978	$203.80	$203.80	$203.80
Purchase #2	$98.93	12.471%	$111.2676	$111.27	$111.25	$111.30
Purchase #3	$90.37	3.270%	$93.3251	$93.33	$93.35	$93.30
Purchase #4	$217.33	10.541%	$240.2388	$240.24	$240.25	$240.20
Purchase #5	$237.83	7.768%	$256.3046	$256.30	$256.30	$256.30
Purchase #6	$176.59	11.230%	$196.4211	$196.42	$196.40	$196.40
Purchase #7	$27.33	6.423%	$29.0854	$29.09	$29.10	$29.10
7 purchase totals =	$1,027.77		$1,130.4404	$1,130.45	$1,130.45	$1,130.40