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 $88.59   7.787%   $95.4885   $95.49   $95.50   $95.50  
  Purchase #2 $160.50   9.132%   $175.1569   $175.16   $175.15   $175.20  
  Purchase #3 $108.46   8.691%   $117.8863   $117.89   $117.90   $117.90  
  Purchase #4 $95.39   7.456%   $102.5023   $102.50   $102.50   $102.50  
  Purchase #5 $228.86   6.189%   $243.0241   $243.02   $243.00   $243.00  
  Purchase #6 $199.95   8.863%   $217.6716   $217.67   $217.65   $217.70  
  Purchase #7 $225.74   8.121%   $244.0723   $244.07   $244.05   $244.10  
  7 purchase totals = $1,107.49       $1,195.8020   $1,195.80   $1,195.75   $1,195.90