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 $149.54   8.290%   $161.9369   $161.94   $161.95   $161.90  
  Purchase #2 $247.95   5.831%   $262.408   $262.41   $262.40   $262.40  
  Purchase #3 $39.69   4.343%   $41.4137   $41.41   $41.40   $41.40  
  Purchase #4 $93.73   4.244%   $97.7079   $97.71   $97.70   $97.70  
  Purchase #5 $211.62   5.312%   $222.8613   $222.86   $222.85   $222.90  
  Purchase #6 $240.74   9.119%   $262.6931   $262.69   $262.70   $262.70  
  Purchase #7 $78.26   9.568%   $85.7479   $85.75   $85.75   $85.70  
  7 purchase totals = $1,061.53       $1,134.7688   $1,134.77   $1,134.75   $1,134.70