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 $163.87   7.451%   $176.08   $176.08   $176.10   $176.10  
  Purchase #2 $68.93   3.838%   $71.5755   $71.58   $71.60   $71.60  
  Purchase #3 $250.70   6.184%   $266.2033   $266.20   $266.20   $266.20  
  Purchase #4 $65.97   5.339%   $69.4921   $69.49   $69.50   $69.50  
  Purchase #5 $174.80   12.242%   $196.199   $196.20   $196.20   $196.20  
  Purchase #6 $132.42   13.269%   $149.9908   $149.99   $150.00   $150.00  
  Purchase #7 $22.64   8.701%   $24.6099   $24.61   $24.60   $24.60  
  7 purchase totals = $879.33       $954.1506   $954.15   $954.20   $954.20