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 $196.58   6.802%   $209.9514   $209.95   $209.95   $210.00  
  Purchase #2 $149.73   5.727%   $158.305   $158.31   $158.30   $158.30  
  Purchase #3 $82.72   12.670%   $93.2006   $93.20   $93.20   $93.20  
  Purchase #4 $34.87   5.121%   $36.6557   $36.66   $36.65   $36.70  
  Purchase #5 $245.54   12.264%   $275.653   $275.65   $275.65   $275.70  
  Purchase #6 $129.88   7.613%   $139.7678   $139.77   $139.75   $139.80  
  Purchase #7 $119.86   11.155%   $133.2304   $133.23   $133.25   $133.20  
  7 purchase totals = $959.18       $1,046.7639   $1,046.77   $1,046.75   $1,046.90