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 $33.61   7.434%   $36.1086   $36.11   $36.10   $36.10  
  Purchase #2 $167.28   9.441%   $183.0729   $183.07   $183.05   $183.10  
  Purchase #3 $93.61   9.714%   $102.7033   $102.70   $102.70   $102.70  
  Purchase #4 $193.82   6.624%   $206.6586   $206.66   $206.65   $206.70  
  Purchase #5 $173.96   10.297%   $191.8727   $191.87   $191.85   $191.90  
  Purchase #6 $247.39   11.533%   $275.9215   $275.92   $275.90   $275.90  
  Purchase #7 $68.76   11.535%   $76.6915   $76.69   $76.70   $76.70  
  7 purchase totals = $978.43       $1,073.0291   $1,073.02   $1,072.95   $1,073.10