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 $55.71   12.415%   $62.6264   $62.63   $62.65   $62.60  
  Purchase #2 $156.81   7.103%   $167.9482   $167.95   $167.95   $167.90  
  Purchase #3 $92.68   3.518%   $95.9405   $95.94   $95.95   $95.90  
  Purchase #4 $219.29   12.397%   $246.4754   $246.48   $246.50   $246.50  
  Purchase #5 $6.93   4.814%   $7.2636   $7.26   $7.25   $7.30  
  Purchase #6 $55.52   6.112%   $58.9134   $58.91   $58.90   $58.90  
  Purchase #7 $53.87   4.788%   $56.4493   $56.45   $56.45   $56.40  
  7 purchase totals = $640.81       $695.6168   $695.62   $695.65   $695.50