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 $56.88   9.392%   $62.2222   $62.22   $62.20   $62.20  
  Purchase #2 $217.37   13.409%   $246.5171   $246.52   $246.50   $246.50  
  Purchase #3 $169.46   12.416%   $190.5002   $190.50   $190.50   $190.50  
  Purchase #4 $180.32   6.428%   $191.911   $191.91   $191.90   $191.90  
  Purchase #5 $30.47   8.683%   $33.1157   $33.12   $33.10   $33.10  
  Purchase #6 $180.45   7.207%   $193.455   $193.46   $193.45   $193.50  
  Purchase #7 $33.73   8.787%   $36.6939   $36.69   $36.70   $36.70  
  7 purchase totals = $868.68       $954.4151   $954.42   $954.35   $954.40