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 $85.94   12.411%   $96.606   $96.61   $96.60   $96.60  
  Purchase #2 $212.97   11.230%   $236.8865   $236.89   $236.90   $236.90  
  Purchase #3 $18.29   11.751%   $20.4393   $20.44   $20.45   $20.40  
  Purchase #4 $83.68   6.792%   $89.3635   $89.36   $89.35   $89.40  
  Purchase #5 $84.76   9.295%   $92.6384   $92.64   $92.65   $92.60  
  Purchase #6 $228.99   7.724%   $246.6772   $246.68   $246.70   $246.70  
  Purchase #7 $17.71   7.839%   $19.0983   $19.10   $19.10   $19.10  
  7 purchase totals = $732.34       $801.7092   $801.72   $801.75   $801.70