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	$112.53	9.741%	$123.4915	$123.49	$123.50	$123.50
Purchase #2	$160.98	4.234%	$167.7959	$167.80	$167.80	$167.80
Purchase #3	$100.34	3.683%	$104.0355	$104.04	$104.05	$104.00
Purchase #4	$149.43	7.618%	$160.8136	$160.81	$160.80	$160.80
Purchase #5	$33.50	9.709%	$36.7525	$36.75	$36.75	$36.80
Purchase #6	$38.83	11.549%	$43.3145	$43.31	$43.30	$43.30
Purchase #7	$163.83	8.711%	$178.1012	$178.10	$178.10	$178.10
7 purchase totals =	$759.44		$814.3047	$814.30	$814.30	$814.30