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 $204.54   9.269%   $223.4988   $223.50   $223.50   $223.50  
  Purchase #2 $116.30   13.448%   $131.94   $131.94   $131.95   $131.90  
  Purchase #3 $97.53   4.790%   $102.2017   $102.20   $102.20   $102.20  
  Purchase #4 $247.93   8.211%   $268.2875   $268.29   $268.30   $268.30  
  Purchase #5 $220.45   4.645%   $230.6899   $230.69   $230.70   $230.70  
  Purchase #6 $89.37   3.293%   $92.313   $92.31   $92.30   $92.30  
  Purchase #7 $113.95   10.158%   $125.525   $125.53   $125.55   $125.50  
  7 purchase totals = $1,090.07       $1,174.4559   $1,174.46   $1,174.50   $1,174.40