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	$59.55	9.755%	$65.3591	$65.36	$65.35	$65.40
Purchase #2	$118.68	10.544%	$131.1936	$131.19	$131.20	$131.20
Purchase #3	$247.30	3.480%	$255.906	$255.91	$255.90	$255.90
Purchase #4	$178.78	4.362%	$186.5784	$186.58	$186.60	$186.60
Purchase #5	$78.40	3.628%	$81.2444	$81.24	$81.25	$81.20
Purchase #6	$93.53	8.553%	$101.5296	$101.53	$101.55	$101.50
Purchase #7	$204.51	11.419%	$227.863	$227.86	$227.85	$227.90
7 purchase totals =	$980.75		$1,049.6741	$1,049.67	$1,049.70	$1,049.70