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 $26.57   10.839%   $29.4499   $29.45   $29.45   $29.40  
  Purchase #2 $83.80   13.362%   $94.9974   $95.00   $95.00   $95.00  
  Purchase #3 $152.53   12.523%   $171.6313   $171.63   $171.65   $171.60  
  Purchase #4 $173.78   9.617%   $190.4924   $190.49   $190.50   $190.50  
  Purchase #5 $244.93   5.378%   $258.1023   $258.10   $258.10   $258.10  
  Purchase #6 $135.73   9.424%   $148.5212   $148.52   $148.50   $148.50  
  Purchase #7 $144.77   8.726%   $157.4026   $157.40   $157.40   $157.40  
  7 purchase totals = $962.11       $1,050.5971   $1,050.59   $1,050.60   $1,050.50