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	$243.44	11.382%	$271.1483	$271.15	$271.15	$271.10
Purchase #2	$154.56	12.243%	$173.4828	$173.48	$173.50	$173.50
Purchase #3	$32.34	6.544%	$34.4563	$34.46	$34.45	$34.50
Purchase #4	$182.92	7.605%	$196.8311	$196.83	$196.85	$196.80
Purchase #5	$196.70	11.744%	$219.8004	$219.80	$219.80	$219.80
Purchase #6	$119.33	4.391%	$124.5698	$124.57	$124.55	$124.60
Purchase #7	$34.29	5.848%	$36.2953	$36.30	$36.30	$36.30
7 purchase totals =	$963.58		$1,056.5840	$1,056.59	$1,056.60	$1,056.60