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	$94.43	4.536%	$98.7133	$98.71	$98.70	$98.70
Purchase #2	$117.61	8.353%	$127.434	$127.43	$127.45	$127.40
Purchase #3	$38.85	3.340%	$40.1476	$40.15	$40.15	$40.10
Purchase #4	$175.98	9.367%	$192.464	$192.46	$192.45	$192.50
Purchase #5	$35.67	6.255%	$37.9012	$37.90	$37.90	$37.90
Purchase #6	$198.38	4.362%	$207.0333	$207.03	$207.05	$207.00
Purchase #7	$41.34	9.833%	$45.405	$45.41	$45.40	$45.40
7 purchase totals =	$702.26		$749.0984	$749.09	$749.10	$749.00