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 $116.39   8.260%   $126.0038   $126.00   $126.00   $126.00  
  Purchase #2 $33.33   7.444%   $35.8111   $35.81   $35.80   $35.80  
  Purchase #3 $162.98   7.108%   $174.5646   $174.56   $174.55   $174.60  
  Purchase #4 $97.58   7.225%   $104.6302   $104.63   $104.65   $104.60  
  Purchase #5 $231.26   12.543%   $260.2669   $260.27   $260.25   $260.30  
  Purchase #6 $163.82   6.760%   $174.8942   $174.89   $174.90   $174.90  
  Purchase #7 $148.30   5.386%   $156.2874   $156.29   $156.30   $156.30  
  7 purchase totals = $953.66       $1,032.4582   $1,032.45   $1,032.45   $1,032.50