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	$92.32	12.708%	$104.052	$104.05	$104.05	$104.10
Purchase #2	$230.74	4.655%	$241.4809	$241.48	$241.50	$241.50
Purchase #3	$82.81	7.347%	$88.8941	$88.89	$88.90	$88.90
Purchase #4	$230.69	6.874%	$246.5476	$246.55	$246.55	$246.50
Purchase #5	$200.90	12.555%	$226.123	$226.12	$226.10	$226.10
Purchase #6	$13.71	12.151%	$15.3759	$15.38	$15.40	$15.40
Purchase #7	$207.54	10.338%	$228.9955	$229.00	$229.00	$229.00
7 purchase totals =	$1,058.71		$1,151.4690	$1,151.47	$1,151.50	$1,151.50