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 $176.40   9.534%   $193.218   $193.22   $193.20   $193.20  
  Purchase #2 $96.94   9.194%   $105.8527   $105.85   $105.85   $105.90  
  Purchase #3 $55.65   7.324%   $59.7258   $59.73   $59.75   $59.70  
  Purchase #4 $184.94   9.767%   $203.0031   $203.00   $203.00   $203.00  
  Purchase #5 $248.54   3.603%   $257.4949   $257.49   $257.50   $257.50  
  Purchase #6 $176.79   7.477%   $190.0086   $190.01   $190.00   $190.00  
  Purchase #7 $154.31   7.121%   $165.2984   $165.30   $165.30   $165.30  
  7 purchase totals = $1,093.57       $1,174.6015   $1,174.60   $1,174.60   $1,174.60