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	$243.35	11.868%	$272.2308	$272.23	$272.25	$272.20
Purchase #2	$115.37	3.274%	$119.1472	$119.15	$119.15	$119.10
Purchase #3	$17.60	7.177%	$18.8632	$18.86	$18.85	$18.90
Purchase #4	$72.71	13.142%	$82.2655	$82.27	$82.25	$82.30
Purchase #5	$198.95	3.184%	$205.2846	$205.28	$205.30	$205.30
Purchase #6	$143.66	13.383%	$162.886	$162.89	$162.90	$162.90
Purchase #7	$174.90	10.168%	$192.6838	$192.68	$192.70	$192.70
7 purchase totals =	$966.54		$1,053.3611	$1,053.36	$1,053.40	$1,053.40