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	$249.25	9.744%	$273.5369	$273.54	$273.55	$273.50
Purchase #2	$165.71	12.524%	$186.4635	$186.46	$186.45	$186.50
Purchase #3	$120.51	5.336%	$126.9404	$126.94	$126.95	$126.90
Purchase #4	$169.63	8.393%	$183.867	$183.87	$183.85	$183.90
Purchase #5	$57.41	3.677%	$59.521	$59.52	$59.50	$59.50
Purchase #6	$189.86	8.512%	$206.0209	$206.02	$206.00	$206.00
Purchase #7	$103.46	4.617%	$108.2367	$108.24	$108.25	$108.20
7 purchase totals =	$1,055.83		$1,144.5864	$1,144.59	$1,144.55	$1,144.50