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	$157.38	5.437%	$165.9368	$165.94	$165.95	$165.90
Purchase #2	$184.89	11.182%	$205.5644	$205.56	$205.55	$205.60
Purchase #3	$214.93	4.168%	$223.8883	$223.89	$223.90	$223.90
Purchase #4	$71.99	8.189%	$77.8853	$77.89	$77.90	$77.90
Purchase #5	$67.67	9.788%	$74.2935	$74.29	$74.30	$74.30
Purchase #6	$136.71	12.775%	$154.1747	$154.17	$154.15	$154.20
Purchase #7	$168.43	9.697%	$184.7627	$184.76	$184.75	$184.80
7 purchase totals =	$1,002.00		$1,086.5057	$1,086.50	$1,086.50	$1,086.60