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	$117.74	11.669%	$131.4791	$131.48	$131.50	$131.50
Purchase #2	$11.53	6.765%	$12.31	$12.31	$12.30	$12.30
Purchase #3	$88.49	11.622%	$98.7743	$98.77	$98.75	$98.80
Purchase #4	$55.46	12.720%	$62.5145	$62.51	$62.50	$62.50
Purchase #5	$9.50	3.819%	$9.8628	$9.86	$9.85	$9.90
Purchase #6	$93.71	4.148%	$97.5971	$97.60	$97.60	$97.60
Purchase #7	$47.48	13.511%	$53.895	$53.90	$53.90	$53.90
7 purchase totals =	$423.91		$466.4328	$466.43	$466.40	$466.50