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	$61.32	3.866%	$63.6906	$63.69	$63.70	$63.70
Purchase #2	$201.25	8.691%	$218.7406	$218.74	$218.75	$218.70
Purchase #3	$118.68	4.108%	$123.5554	$123.56	$123.55	$123.60
Purchase #4	$56.25	6.145%	$59.7066	$59.71	$59.70	$59.70
Purchase #5	$133.79	8.327%	$144.9307	$144.93	$144.95	$144.90
Purchase #6	$100.45	6.236%	$106.7141	$106.71	$106.70	$106.70
Purchase #7	$43.33	4.206%	$45.1525	$45.15	$45.15	$45.20
7 purchase totals =	$715.07		$762.4905	$762.49	$762.50	$762.50