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	$220.37	4.492%	$230.269	$230.27	$230.25	$230.30
Purchase #2	$127.78	10.243%	$140.8685	$140.87	$140.85	$140.90
Purchase #3	$42.59	3.112%	$43.9154	$43.92	$43.90	$43.90
Purchase #4	$171.44	9.115%	$187.0668	$187.07	$187.05	$187.10
Purchase #5	$188.33	12.808%	$212.4513	$212.45	$212.45	$212.50
Purchase #6	$19.37	12.696%	$21.8292	$21.83	$21.85	$21.80
Purchase #7	$248.98	3.837%	$258.5334	$258.53	$258.55	$258.50
7 purchase totals =	$1,018.86		$1,094.9336	$1,094.94	$1,094.90	$1,095.00