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 $67.76   13.157%   $76.6752   $76.68   $76.70   $76.70  
  Purchase #2 $157.31   6.598%   $167.6893   $167.69   $167.70   $167.70  
  Purchase #3 $88.59   8.629%   $96.2344   $96.23   $96.25   $96.20  
  Purchase #4 $148.89   12.500%   $167.5013   $167.50   $167.50   $167.50  
  Purchase #5 $223.52   8.597%   $242.736   $242.74   $242.75   $242.70  
  Purchase #6 $166.95   3.731%   $173.1789   $173.18   $173.20   $173.20  
  Purchase #7 $36.84   3.378%   $38.0845   $38.08   $38.10   $38.10  
  7 purchase totals = $889.86       $962.0996   $962.10   $962.20   $962.10