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 $176.63   11.222%   $196.4514   $196.45   $196.45   $196.50  
  Purchase #2 $187.84   3.295%   $194.0293   $194.03   $194.05   $194.00  
  Purchase #3 $22.70   10.165%   $25.0075   $25.01   $25.00   $25.00  
  Purchase #4 $78.66   10.358%   $86.8076   $86.81   $86.80   $86.80  
  Purchase #5 $174.46   12.281%   $195.8854   $195.89   $195.90   $195.90  
  Purchase #6 $110.40   12.299%   $123.9781   $123.98   $124.00   $124.00  
  Purchase #7 $230.37   3.221%   $237.7902   $237.79   $237.80   $237.80  
  7 purchase totals = $981.06       $1,059.9495   $1,059.96   $1,060.00   $1,060.00