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 $216.85   8.488%   $235.2562   $235.26   $235.25   $235.30  
  Purchase #2 $136.31   13.245%   $154.3643   $154.36   $154.35   $154.40  
  Purchase #3 $62.82   6.366%   $66.8191   $66.82   $66.80   $66.80  
  Purchase #4 $106.73   13.717%   $121.3702   $121.37   $121.35   $121.40  
  Purchase #5 $241.81   10.287%   $266.685   $266.69   $266.70   $266.70  
  Purchase #6 $246.54   7.153%   $264.175   $264.18   $264.20   $264.20  
  Purchase #7 $77.66   12.725%   $87.5422   $87.54   $87.55   $87.50  
  7 purchase totals = $1,088.72       $1,196.2120   $1,196.22   $1,196.20   $1,196.30