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	$132.62	4.828%	$139.0229	$139.02	$139.00	$139.00
Purchase #2	$134.63	13.326%	$152.5708	$152.57	$152.55	$152.60
Purchase #3	$108.74	13.621%	$123.5515	$123.55	$123.55	$123.60
Purchase #4	$133.64	3.287%	$138.0327	$138.03	$138.05	$138.00
Purchase #5	$57.46	6.471%	$61.1782	$61.18	$61.20	$61.20
Purchase #6	$62.87	13.360%	$71.2694	$71.27	$71.25	$71.30
Purchase #7	$239.53	9.412%	$262.0746	$262.07	$262.05	$262.10
7 purchase totals =	$869.49		$947.7001	$947.69	$947.65	$947.80