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 $56.75   10.325%   $62.6094   $62.61   $62.60   $62.60  
  Purchase #2 $163.58   5.835%   $173.1249   $173.12   $173.10   $173.10  
  Purchase #3 $66.57   12.568%   $74.9365   $74.94   $74.95   $74.90  
  Purchase #4 $152.65   12.633%   $171.9343   $171.93   $171.95   $171.90  
  Purchase #5 $183.98   12.544%   $207.0585   $207.06   $207.05   $207.10  
  Purchase #6 $190.70   11.441%   $212.518   $212.52   $212.50   $212.50  
  Purchase #7 $30.40   4.238%   $31.6884   $31.69   $31.70   $31.70  
  7 purchase totals = $844.63       $933.8700   $933.87   $933.85   $933.80