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	$245.80	3.860%	$255.2879	$255.29	$255.30	$255.30
Purchase #2	$229.99	6.509%	$244.96	$244.96	$244.95	$245.00
Purchase #3	$12.44	9.398%	$13.6091	$13.61	$13.60	$13.60
Purchase #4	$51.60	3.541%	$53.4272	$53.43	$53.45	$53.40
Purchase #5	$94.88	10.169%	$104.5283	$104.53	$104.55	$104.50
Purchase #6	$203.81	3.481%	$210.9046	$210.90	$210.90	$210.90
Purchase #7	$38.31	11.190%	$42.5969	$42.60	$42.60	$42.60
7 purchase totals =	$876.83		$925.3140	$925.32	$925.35	$925.30