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	$43.86	3.327%	$45.3192	$45.32	$45.30	$45.30
Purchase #2	$197.63	7.522%	$212.4957	$212.50	$212.50	$212.50
Purchase #3	$35.35	12.808%	$39.8776	$39.88	$39.90	$39.90
Purchase #4	$47.73	8.522%	$51.7976	$51.80	$51.80	$51.80
Purchase #5	$39.89	6.419%	$42.4505	$42.45	$42.45	$42.50
Purchase #6	$31.60	6.364%	$33.611	$33.61	$33.60	$33.60
Purchase #7	$209.29	4.486%	$218.6787	$218.68	$218.70	$218.70
7 purchase totals =	$605.35		$644.2303	$644.24	$644.25	$644.30