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	$221.81	13.746%	$252.3	$252.30	$252.30	$252.30
Purchase #2	$226.41	10.683%	$250.5974	$250.60	$250.60	$250.60
Purchase #3	$222.45	11.578%	$248.2053	$248.21	$248.20	$248.20
Purchase #4	$89.57	3.273%	$92.5016	$92.50	$92.50	$92.50
Purchase #5	$71.93	7.720%	$77.483	$77.48	$77.50	$77.50
Purchase #6	$12.53	10.145%	$13.8012	$13.80	$13.80	$13.80
Purchase #7	$141.90	7.738%	$152.8802	$152.88	$152.90	$152.90
7 purchase totals =	$986.60		$1,087.7687	$1,087.77	$1,087.80	$1,087.80