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	$237.29	9.484%	$259.7946	$259.79	$259.80	$259.80
Purchase #2	$222.87	5.831%	$235.8655	$235.87	$235.85	$235.90
Purchase #3	$238.34	13.682%	$270.9497	$270.95	$270.95	$270.90
Purchase #4	$174.95	3.401%	$180.9	$180.90	$180.90	$180.90
Purchase #5	$93.72	10.314%	$103.3863	$103.39	$103.40	$103.40
Purchase #6	$73.41	7.285%	$78.7579	$78.76	$78.75	$78.80
Purchase #7	$11.31	5.755%	$11.9609	$11.96	$11.95	$12.00
7 purchase totals =	$1,051.89		$1,141.6149	$1,141.62	$1,141.60	$1,141.70