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 $192.66   4.343%   $201.0272   $201.03   $201.05   $201.00  
  Purchase #2 $223.81   10.434%   $247.1623   $247.16   $247.15   $247.20  
  Purchase #3 $60.72   11.604%   $67.7659   $67.77   $67.75   $67.80  
  Purchase #4 $106.85   3.441%   $110.5267   $110.53   $110.55   $110.50  
  Purchase #5 $181.67   13.498%   $206.1918   $206.19   $206.20   $206.20  
  Purchase #6 $48.31   7.579%   $51.9714   $51.97   $51.95   $52.00  
  Purchase #7 $224.41   11.845%   $250.9914   $250.99   $251.00   $251.00  
  7 purchase totals = $1,038.43       $1,135.6367   $1,135.64   $1,135.65   $1,135.70