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	$181.31	3.173%	$187.063	$187.06	$187.05	$187.10
Purchase #2	$123.29	8.602%	$133.8954	$133.90	$133.90	$133.90
Purchase #3	$233.59	12.143%	$261.9548	$261.95	$261.95	$262.00
Purchase #4	$117.67	3.103%	$121.3213	$121.32	$121.30	$121.30
Purchase #5	$117.90	5.764%	$124.6958	$124.70	$124.70	$124.70
Purchase #6	$59.85	13.555%	$67.9627	$67.96	$67.95	$68.00
Purchase #7	$151.33	8.759%	$164.585	$164.59	$164.60	$164.60
7 purchase totals =	$984.94		$1,061.4780	$1,061.48	$1,061.45	$1,061.60