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 $116.34   8.820%   $126.6012   $126.60   $126.60   $126.60  
  Purchase #2 $95.91   12.293%   $107.7002   $107.70   $107.70   $107.70  
  Purchase #3 $249.88   13.807%   $284.3809   $284.38   $284.40   $284.40  
  Purchase #4 $86.31   8.502%   $93.6481   $93.65   $93.65   $93.60  
  Purchase #5 $161.33   13.195%   $182.6175   $182.62   $182.60   $182.60  
  Purchase #6 $77.26   9.764%   $84.8037   $84.80   $84.80   $84.80  
  Purchase #7 $166.29   8.661%   $180.6924   $180.69   $180.70   $180.70  
  7 purchase totals = $953.32       $1,060.4440   $1,060.44   $1,060.45   $1,060.40