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	$228.53	13.118%	$258.5086	$258.51	$258.50	$258.50
Purchase #2	$221.50	3.254%	$228.7076	$228.71	$228.70	$228.70
Purchase #3	$5.53	11.782%	$6.1815	$6.18	$6.20	$6.20
Purchase #4	$140.87	12.716%	$158.783	$158.78	$158.80	$158.80
Purchase #5	$168.54	3.348%	$174.1827	$174.18	$174.20	$174.20
Purchase #6	$164.82	10.175%	$181.5904	$181.59	$181.60	$181.60
Purchase #7	$74.90	5.377%	$78.9274	$78.93	$78.95	$78.90
7 purchase totals =	$1,004.69		$1,086.8812	$1,086.88	$1,086.95	$1,086.90