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	$162.37	5.697%	$171.6202	$171.62	$171.60	$171.60
Purchase #2	$216.68	10.248%	$238.8854	$238.89	$238.90	$238.90
Purchase #3	$63.39	4.299%	$66.1151	$66.12	$66.10	$66.10
Purchase #4	$220.34	4.708%	$230.7136	$230.71	$230.70	$230.70
Purchase #5	$90.43	12.602%	$101.826	$101.83	$101.85	$101.80
Purchase #6	$58.66	13.386%	$66.5122	$66.51	$66.50	$66.50
Purchase #7	$166.44	12.824%	$187.7843	$187.78	$187.80	$187.80
7 purchase totals =	$978.31		$1,063.4568	$1,063.46	$1,063.45	$1,063.40