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	$131.48	7.184%	$140.9255	$140.93	$140.95	$140.90
Purchase #2	$21.33	7.561%	$22.9428	$22.94	$22.95	$22.90
Purchase #3	$192.94	3.800%	$200.2717	$200.27	$200.25	$200.30
Purchase #4	$221.82	8.654%	$241.0163	$241.02	$241.00	$241.00
Purchase #5	$201.47	8.866%	$219.3323	$219.33	$219.35	$219.30
Purchase #6	$162.94	10.294%	$179.713	$179.71	$179.70	$179.70
Purchase #7	$50.92	4.578%	$53.2511	$53.25	$53.25	$53.30
7 purchase totals =	$982.90		$1,057.4527	$1,057.45	$1,057.45	$1,057.40