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	$208.25	11.352%	$231.8905	$231.89	$231.90	$231.90
Purchase #2	$242.32	9.497%	$265.3331	$265.33	$265.35	$265.30
Purchase #3	$95.57	3.124%	$98.5556	$98.56	$98.55	$98.60
Purchase #4	$174.41	3.429%	$180.3905	$180.39	$180.40	$180.40
Purchase #5	$152.66	4.592%	$159.6701	$159.67	$159.65	$159.70
Purchase #6	$158.60	8.293%	$171.7527	$171.75	$171.75	$171.80
Purchase #7	$102.86	6.272%	$109.3114	$109.31	$109.30	$109.30
7 purchase totals =	$1,134.67		$1,216.9039	$1,216.90	$1,216.90	$1,217.00