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 $59.82   4.220%   $62.3444   $62.34   $62.35   $62.30  
  Purchase #2 $203.41   5.537%   $214.6728   $214.67   $214.65   $214.70  
  Purchase #3 $9.58   11.555%   $10.687   $10.69   $10.70   $10.70  
  Purchase #4 $180.40   5.343%   $190.0388   $190.04   $190.05   $190.00  
  Purchase #5 $40.93   11.215%   $45.5203   $45.52   $45.50   $45.50  
  Purchase #6 $149.63   8.816%   $162.8214   $162.82   $162.80   $162.80  
  Purchase #7 $200.31   4.342%   $209.0075   $209.01   $209.00   $209.00  
  7 purchase totals = $844.08       $895.0922   $895.09   $895.05   $895.00