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 $118.60   5.542%   $125.1728   $125.17   $125.15   $125.20  
  Purchase #2 $39.46   9.743%   $43.3046   $43.30   $43.30   $43.30  
  Purchase #3 $220.83   9.123%   $240.9763   $240.98   $241.00   $241.00  
  Purchase #4 $243.34   5.812%   $257.4829   $257.48   $257.50   $257.50  
  Purchase #5 $55.50   10.805%   $61.4968   $61.50   $61.50   $61.50  
  Purchase #6 $143.75   7.319%   $154.2711   $154.27   $154.25   $154.30  
  Purchase #7 $172.92   11.359%   $192.562   $192.56   $192.55   $192.60  
  7 purchase totals = $994.40       $1,075.2665   $1,075.26   $1,075.25   $1,075.40