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	$93.76	3.611%	$97.1457	$97.15	$97.15	$97.10
Purchase #2	$172.45	7.578%	$185.5183	$185.52	$185.50	$185.50
Purchase #3	$154.61	4.359%	$161.3494	$161.35	$161.35	$161.30
Purchase #4	$250.51	8.338%	$271.3975	$271.40	$271.40	$271.40
Purchase #5	$183.51	3.538%	$190.0026	$190.00	$190.00	$190.00
Purchase #6	$97.49	7.284%	$104.5912	$104.59	$104.60	$104.60
Purchase #7	$95.36	7.486%	$102.4986	$102.50	$102.50	$102.50
7 purchase totals =	$1,047.69		$1,112.5033	$1,112.51	$1,112.50	$1,112.40