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 $136.77   11.847%   $152.9731   $152.97   $152.95   $153.00  
  Purchase #2 $100.29   7.474%   $107.7857   $107.79   $107.80   $107.80  
  Purchase #3 $90.26   8.410%   $97.8509   $97.85   $97.85   $97.90  
  Purchase #4 $223.95   3.524%   $231.842   $231.84   $231.85   $231.80  
  Purchase #5 $204.32   5.416%   $215.386   $215.39   $215.40   $215.40  
  Purchase #6 $187.31   5.272%   $197.185   $197.19   $197.20   $197.20  
  Purchase #7 $10.66   9.684%   $11.6923   $11.69   $11.70   $11.70  
  7 purchase totals = $953.56       $1,014.7150   $1,014.72   $1,014.75   $1,014.80