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	$211.55	5.870%	$223.968	$223.97	$223.95	$224.00
Purchase #2	$68.51	11.631%	$76.4784	$76.48	$76.50	$76.50
Purchase #3	$48.46	3.493%	$50.1527	$50.15	$50.15	$50.20
Purchase #4	$145.84	8.223%	$157.8324	$157.83	$157.85	$157.80
Purchase #5	$66.75	6.762%	$71.2636	$71.26	$71.25	$71.30
Purchase #6	$36.25	11.208%	$40.3129	$40.31	$40.30	$40.30
Purchase #7	$31.94	10.597%	$35.3247	$35.32	$35.30	$35.30
7 purchase totals =	$609.30		$655.3327	$655.32	$655.30	$655.40