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	$215.62	4.531%	$225.3897	$225.39	$225.40	$225.40
Purchase #2	$113.72	5.351%	$119.8052	$119.81	$119.80	$119.80
Purchase #3	$187.61	8.779%	$204.0803	$204.08	$204.10	$204.10
Purchase #4	$164.53	5.534%	$173.6351	$173.64	$173.65	$173.60
Purchase #5	$91.57	9.778%	$100.5237	$100.52	$100.50	$100.50
Purchase #6	$76.30	11.676%	$85.2088	$85.21	$85.20	$85.20
Purchase #7	$119.39	5.441%	$125.886	$125.89	$125.90	$125.90
7 purchase totals =	$968.74		$1,034.5288	$1,034.54	$1,034.55	$1,034.50