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 $89.83   6.344%   $95.5288   $95.53   $95.55   $95.50  
  Purchase #2 $103.93   12.814%   $117.2476   $117.25   $117.25   $117.20  
  Purchase #3 $181.49   7.277%   $194.697   $194.70   $194.70   $194.70  
  Purchase #4 $205.80   8.526%   $223.3465   $223.35   $223.35   $223.30  
  Purchase #5 $116.84   13.575%   $132.701   $132.70   $132.70   $132.70  
  Purchase #6 $163.39   13.874%   $186.0587   $186.06   $186.05   $186.10  
  Purchase #7 $53.93   12.785%   $60.825   $60.83   $60.85   $60.80  
  7 purchase totals = $915.21       $1,010.4046   $1,010.42   $1,010.45   $1,010.30