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 $228.48   7.505%   $245.6274   $245.63   $245.65   $245.60  
  Purchase #2 $193.91   4.601%   $202.8318   $202.83   $202.85   $202.80  
  Purchase #3 $13.89   8.434%   $15.0615   $15.06   $15.05   $15.10  
  Purchase #4 $53.56   9.140%   $58.4554   $58.46   $58.45   $58.50  
  Purchase #5 $77.51   4.458%   $80.9654   $80.97   $80.95   $81.00  
  Purchase #6 $220.97   4.743%   $231.4506   $231.45   $231.45   $231.50  
  Purchase #7 $237.46   12.654%   $267.5082   $267.51   $267.50   $267.50  
  7 purchase totals = $1,025.78       $1,101.9003   $1,101.91   $1,101.90   $1,102.00