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 $91.87   3.476%   $95.0634   $95.06   $95.05   $95.10  
  Purchase #2 $200.79   3.271%   $207.3578   $207.36   $207.35   $207.40  
  Purchase #3 $199.85   8.294%   $216.4256   $216.43   $216.45   $216.40  
  Purchase #4 $117.26   5.643%   $123.877   $123.88   $123.90   $123.90  
  Purchase #5 $168.52   7.293%   $180.8102   $180.81   $180.80   $180.80  
  Purchase #6 $109.33   13.122%   $123.6763   $123.68   $123.70   $123.70  
  Purchase #7 $151.89   5.753%   $160.6282   $160.63   $160.65   $160.60  
  7 purchase totals = $1,039.51       $1,107.8385   $1,107.85   $1,107.90   $1,107.90