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 $88.31   7.806%   $95.2035   $95.20   $95.20   $95.20  
  Purchase #2 $34.49   3.533%   $35.7085   $35.71   $35.70   $35.70  
  Purchase #3 $174.51   9.153%   $190.4829   $190.48   $190.50   $190.50  
  Purchase #4 $93.55   6.482%   $99.6139   $99.61   $99.60   $99.60  
  Purchase #5 $194.49   5.181%   $204.5665   $204.57   $204.55   $204.60  
  Purchase #6 $206.46   9.617%   $226.3153   $226.32   $226.30   $226.30  
  Purchase #7 $179.34   12.248%   $201.3056   $201.31   $201.30   $201.30  
  7 purchase totals = $971.15       $1,053.1962   $1,053.20   $1,053.15   $1,053.20