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 $216.78   11.454%   $241.61   $241.61   $241.60   $241.60  
  Purchase #2 $111.92   11.870%   $125.2049   $125.20   $125.20   $125.20  
  Purchase #3 $91.44   9.382%   $100.0189   $100.02   $100.00   $100.00  
  Purchase #4 $9.86   8.533%   $10.7014   $10.70   $10.70   $10.70  
  Purchase #5 $78.74   8.777%   $85.651   $85.65   $85.65   $85.70  
  Purchase #6 $172.29   13.498%   $195.5457   $195.55   $195.55   $195.50  
  Purchase #7 $7.98   4.241%   $8.3184   $8.32   $8.30   $8.30  
  7 purchase totals = $689.01       $767.0503   $767.05   $767.00   $767.00