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	$101.69	10.549%	$112.4173	$112.42	$112.40	$112.40
Purchase #2	$168.68	11.240%	$187.6396	$187.64	$187.65	$187.60
Purchase #3	$123.71	10.851%	$137.1338	$137.13	$137.15	$137.10
Purchase #4	$96.39	7.474%	$103.5942	$103.59	$103.60	$103.60
Purchase #5	$90.49	4.269%	$94.353	$94.35	$94.35	$94.40
Purchase #6	$80.36	5.665%	$84.9124	$84.91	$84.90	$84.90
Purchase #7	$97.55	7.859%	$105.2165	$105.22	$105.20	$105.20
7 purchase totals =	$758.87		$825.2668	$825.26	$825.25	$825.20