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	$242.27	7.270%	$259.883	$259.88	$259.90	$259.90
Purchase #2	$245.70	6.411%	$261.4518	$261.45	$261.45	$261.50
Purchase #3	$148.83	13.426%	$168.8119	$168.81	$168.80	$168.80
Purchase #4	$150.78	9.336%	$164.8568	$164.86	$164.85	$164.90
Purchase #5	$45.41	12.780%	$51.2134	$51.21	$51.20	$51.20
Purchase #6	$225.39	4.223%	$234.9082	$234.91	$234.90	$234.90
Purchase #7	$185.33	13.709%	$210.7369	$210.74	$210.75	$210.70
7 purchase totals =	$1,243.71		$1,351.8620	$1,351.86	$1,351.85	$1,351.90