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	$88.90	10.171%	$97.942	$97.94	$97.95	$97.90
Purchase #2	$240.77	7.722%	$259.3623	$259.36	$259.35	$259.40
Purchase #3	$109.71	7.520%	$117.9602	$117.96	$117.95	$118.00
Purchase #4	$74.69	12.226%	$83.8216	$83.82	$83.80	$83.80
Purchase #5	$141.59	3.497%	$146.5414	$146.54	$146.55	$146.50
Purchase #6	$83.40	8.188%	$90.2288	$90.23	$90.25	$90.20
Purchase #7	$80.70	8.526%	$87.5805	$87.58	$87.60	$87.60
7 purchase totals =	$819.76		$883.4368	$883.43	$883.45	$883.40