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	$111.63	13.531%	$126.7347	$126.73	$126.75	$126.70
Purchase #2	$154.54	10.872%	$171.3416	$171.34	$171.35	$171.30
Purchase #3	$37.52	12.165%	$42.0843	$42.08	$42.10	$42.10
Purchase #4	$172.50	5.350%	$181.7288	$181.73	$181.75	$181.70
Purchase #5	$49.39	9.259%	$53.963	$53.96	$53.95	$54.00
Purchase #6	$250.32	6.176%	$265.7798	$265.78	$265.80	$265.80
Purchase #7	$20.35	4.663%	$21.2989	$21.30	$21.30	$21.30
7 purchase totals =	$796.25		$862.9311	$862.92	$863.00	$862.90