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 $52.95   7.511%   $56.9271   $56.93   $56.95   $56.90  
  Purchase #2 $167.48   12.281%   $188.0482   $188.05   $188.05   $188.00  
  Purchase #3 $82.78   8.448%   $89.7733   $89.77   $89.75   $89.80  
  Purchase #4 $162.61   4.418%   $169.7941   $169.79   $169.80   $169.80  
  Purchase #5 $119.93   5.782%   $126.8644   $126.86   $126.85   $126.90  
  Purchase #6 $94.90   7.434%   $101.9549   $101.95   $101.95   $102.00  
  Purchase #7 $72.44   7.295%   $77.7245   $77.72   $77.70   $77.70  
  7 purchase totals = $753.09       $811.0865   $811.07   $811.05   $811.10