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 $58.94   6.325%   $62.668   $62.67   $62.65   $62.70  
  Purchase #2 $228.55   12.719%   $257.6193   $257.62   $257.60   $257.60  
  Purchase #3 $75.68   5.660%   $79.9635   $79.96   $79.95   $80.00  
  Purchase #4 $85.31   3.389%   $88.2012   $88.20   $88.20   $88.20  
  Purchase #5 $202.55   7.787%   $218.3226   $218.32   $218.30   $218.30  
  Purchase #6 $168.65   10.211%   $185.8709   $185.87   $185.85   $185.90  
  Purchase #7 $45.54   10.630%   $50.3809   $50.38   $50.40   $50.40  
  7 purchase totals = $865.22       $943.0264   $943.02   $942.95   $943.10