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 $59.84   5.316%   $63.0211   $63.02   $63.00   $63.00  
  Purchase #2 $216.34   9.386%   $236.6457   $236.65   $236.65   $236.60  
  Purchase #3 $182.48   8.266%   $197.5638   $197.56   $197.55   $197.60  
  Purchase #4 $220.88   7.488%   $237.4195   $237.42   $237.40   $237.40  
  Purchase #5 $185.99   3.156%   $191.8598   $191.86   $191.85   $191.90  
  Purchase #6 $11.37   12.434%   $12.7837   $12.78   $12.80   $12.80  
  Purchase #7 $169.82   5.710%   $179.5167   $179.52   $179.50   $179.50  
  7 purchase totals = $1,046.72       $1,118.8103   $1,118.81   $1,118.75   $1,118.80