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 $61.68   10.197%   $67.9695   $67.97   $67.95   $68.00  
  Purchase #2 $112.78   10.517%   $124.6411   $124.64   $124.65   $124.60  
  Purchase #3 $199.80   6.532%   $212.8509   $212.85   $212.85   $212.90  
  Purchase #4 $180.93   12.709%   $203.9244   $203.92   $203.90   $203.90  
  Purchase #5 $120.93   5.763%   $127.8992   $127.90   $127.90   $127.90  
  Purchase #6 $137.62   4.419%   $143.7014   $143.70   $143.70   $143.70  
  Purchase #7 $138.98   3.647%   $144.0486   $144.05   $144.05   $144.00  
  7 purchase totals = $952.72       $1,025.0351   $1,025.03   $1,025.00   $1,025.00