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	$51.51	5.297%	$54.2385	$54.24	$54.25	$54.20
Purchase #2	$217.46	3.695%	$225.4951	$225.50	$225.50	$225.50
Purchase #3	$62.41	6.579%	$66.516	$66.52	$66.50	$66.50
Purchase #4	$233.62	13.466%	$265.0793	$265.08	$265.10	$265.10
Purchase #5	$191.69	6.126%	$203.4329	$203.43	$203.45	$203.40
Purchase #6	$91.47	12.298%	$102.719	$102.72	$102.70	$102.70
Purchase #7	$80.69	6.255%	$85.7372	$85.74	$85.75	$85.70
7 purchase totals =	$928.85		$1,003.2180	$1,003.23	$1,003.25	$1,003.10