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	$109.56	3.143%	$113.0035	$113.00	$113.00	$113.00
Purchase #2	$198.82	3.277%	$205.3353	$205.34	$205.35	$205.30
Purchase #3	$99.61	10.324%	$109.8937	$109.89	$109.90	$109.90
Purchase #4	$20.89	4.334%	$21.7954	$21.80	$21.80	$21.80
Purchase #5	$112.92	3.727%	$117.1285	$117.13	$117.15	$117.10
Purchase #6	$26.84	5.336%	$28.2722	$28.27	$28.25	$28.30
Purchase #7	$194.98	5.560%	$205.8209	$205.82	$205.80	$205.80
7 purchase totals =	$763.62		$801.2495	$801.25	$801.25	$801.20