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	$41.85	4.157%	$43.5897	$43.59	$43.60	$43.60
Purchase #2	$66.65	6.686%	$71.1062	$71.11	$71.10	$71.10
Purchase #3	$211.36	10.630%	$233.8276	$233.83	$233.85	$233.80
Purchase #4	$91.66	12.455%	$103.0763	$103.08	$103.10	$103.10
Purchase #5	$39.89	6.341%	$42.4194	$42.42	$42.40	$42.40
Purchase #6	$123.44	8.570%	$134.0188	$134.02	$134.00	$134.00
Purchase #7	$141.32	13.300%	$160.1156	$160.12	$160.10	$160.10
7 purchase totals =	$716.17		$788.1536	$788.17	$788.15	$788.10