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	$92.57	10.764%	$102.5342	$102.53	$102.55	$102.50
Purchase #2	$112.67	7.861%	$121.527	$121.53	$121.55	$121.50
Purchase #3	$158.45	11.106%	$176.0475	$176.05	$176.05	$176.00
Purchase #4	$154.40	11.724%	$172.5019	$172.50	$172.50	$172.50
Purchase #5	$166.96	13.142%	$188.9019	$188.90	$188.90	$188.90
Purchase #6	$138.64	4.770%	$145.2531	$145.25	$145.25	$145.30
Purchase #7	$101.61	11.659%	$113.4567	$113.46	$113.45	$113.50
7 purchase totals =	$925.30		$1,020.2223	$1,020.22	$1,020.25	$1,020.20