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	$54.39	13.637%	$61.8072	$61.81	$61.80	$61.80
Purchase #2	$235.96	9.789%	$259.0581	$259.06	$259.05	$259.10
Purchase #3	$190.32	8.156%	$205.8425	$205.84	$205.85	$205.80
Purchase #4	$156.31	6.839%	$167	$167.00	$167.00	$167.00
Purchase #5	$55.66	9.692%	$61.0546	$61.05	$61.05	$61.10
Purchase #6	$40.83	12.234%	$45.8251	$45.83	$45.85	$45.80
Purchase #7	$187.57	10.284%	$206.8597	$206.86	$206.85	$206.90
7 purchase totals =	$921.04		$1,007.4472	$1,007.45	$1,007.45	$1,007.50