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 $59.26   4.832%   $62.1234   $62.12   $62.10   $62.10  
  Purchase #2 $190.58   7.169%   $204.2427   $204.24   $204.25   $204.20  
  Purchase #3 $84.89   3.745%   $88.0691   $88.07   $88.05   $88.10  
  Purchase #4 $207.72   11.108%   $230.7935   $230.79   $230.80   $230.80  
  Purchase #5 $144.92   8.575%   $157.3469   $157.35   $157.35   $157.30  
  Purchase #6 $131.32   11.452%   $146.3588   $146.36   $146.35   $146.40  
  Purchase #7 $173.30   7.852%   $186.9075   $186.91   $186.90   $186.90  
  7 purchase totals = $991.99       $1,075.8419   $1,075.84   $1,075.80   $1,075.80