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	$238.72	11.641%	$266.5094	$266.51	$266.50	$266.50
Purchase #2	$203.40	6.334%	$216.2834	$216.28	$216.30	$216.30
Purchase #3	$40.78	5.645%	$43.082	$43.08	$43.10	$43.10
Purchase #4	$192.37	3.774%	$199.63	$199.63	$199.65	$199.60
Purchase #5	$138.75	3.872%	$144.1224	$144.12	$144.10	$144.10
Purchase #6	$71.65	6.381%	$76.222	$76.22	$76.20	$76.20
Purchase #7	$28.65	11.103%	$31.831	$31.83	$31.85	$31.80
7 purchase totals =	$914.32		$977.6802	$977.67	$977.70	$977.60