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	$118.43	7.291%	$127.0647	$127.06	$127.05	$127.10
Purchase #2	$112.92	12.736%	$127.3015	$127.30	$127.30	$127.30
Purchase #3	$197.97	12.176%	$222.0748	$222.07	$222.05	$222.10
Purchase #4	$13.54	4.688%	$14.1748	$14.17	$14.15	$14.20
Purchase #5	$247.80	9.481%	$271.2939	$271.29	$271.30	$271.30
Purchase #6	$219.74	7.648%	$236.5457	$236.55	$236.55	$236.50
Purchase #7	$180.45	13.822%	$205.3918	$205.39	$205.40	$205.40
7 purchase totals =	$1,090.85		$1,203.8472	$1,203.83	$1,203.80	$1,203.90