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	$202.32	4.493%	$211.4102	$211.41	$211.40	$211.40
Purchase #2	$105.91	3.142%	$109.2377	$109.24	$109.25	$109.20
Purchase #3	$224.89	9.619%	$246.5222	$246.52	$246.50	$246.50
Purchase #4	$137.46	9.392%	$150.3702	$150.37	$150.35	$150.40
Purchase #5	$84.87	5.493%	$89.5319	$89.53	$89.55	$89.50
Purchase #6	$31.52	10.612%	$34.8649	$34.86	$34.85	$34.90
Purchase #7	$196.51	9.699%	$215.5695	$215.57	$215.55	$215.60
7 purchase totals =	$983.48		$1,057.5066	$1,057.50	$1,057.45	$1,057.50