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 $119.62   5.224%   $125.8689   $125.87   $125.85   $125.90  
  Purchase #2 $153.48   4.644%   $160.6076   $160.61   $160.60   $160.60  
  Purchase #3 $247.61   3.566%   $256.4398   $256.44   $256.45   $256.40  
  Purchase #4 $69.57   8.145%   $75.2365   $75.24   $75.25   $75.20  
  Purchase #5 $155.80   10.379%   $171.9705   $171.97   $171.95   $172.00  
  Purchase #6 $224.31   3.155%   $231.387   $231.39   $231.40   $231.40  
  Purchase #7 $102.78   10.276%   $113.3417   $113.34   $113.35   $113.30  
  7 purchase totals = $1,073.17       $1,134.8520   $1,134.86   $1,134.85   $1,134.80