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	$211.81	13.697%	$240.8216	$240.82	$240.80	$240.80
Purchase #2	$164.57	12.163%	$184.5866	$184.59	$184.60	$184.60
Purchase #3	$77.94	11.497%	$86.9008	$86.90	$86.90	$86.90
Purchase #4	$112.93	13.733%	$128.4387	$128.44	$128.45	$128.40
Purchase #5	$118.99	10.324%	$131.2745	$131.27	$131.25	$131.30
Purchase #6	$55.29	6.372%	$58.8131	$58.81	$58.80	$58.80
Purchase #7	$135.78	11.741%	$151.7219	$151.72	$151.70	$151.70
7 purchase totals =	$877.31		$982.5572	$982.55	$982.50	$982.50