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	$195.56	6.652%	$208.5687	$208.57	$208.55	$208.60
Purchase #2	$123.91	10.146%	$136.4819	$136.48	$136.50	$136.50
Purchase #3	$20.54	6.169%	$21.8071	$21.81	$21.80	$21.80
Purchase #4	$153.35	13.820%	$174.543	$174.54	$174.55	$174.50
Purchase #5	$87.29	4.789%	$91.4703	$91.47	$91.45	$91.50
Purchase #6	$179.76	4.871%	$188.5161	$188.52	$188.50	$188.50
Purchase #7	$175.97	6.749%	$187.8462	$187.85	$187.85	$187.80
7 purchase totals =	$936.38		$1,009.2333	$1,009.24	$1,009.20	$1,009.20