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 $218.41   7.596%   $235.0004   $235.00   $235.00   $235.00  
  Purchase #2 $55.61   11.475%   $61.9912   $61.99   $62.00   $62.00  
  Purchase #3 $139.56   6.682%   $148.8854   $148.89   $148.90   $148.90  
  Purchase #4 $218.94   4.698%   $229.2258   $229.23   $229.25   $229.20  
  Purchase #5 $5.79   9.510%   $6.3406   $6.34   $6.35   $6.30  
  Purchase #6 $118.71   4.179%   $123.6709   $123.67   $123.65   $123.70  
  Purchase #7 $39.49   5.611%   $41.7058   $41.71   $41.70   $41.70  
  7 purchase totals = $796.51       $846.8201   $846.83   $846.85   $846.80