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 $182.87   7.581%   $196.7334   $196.73   $196.75   $196.70  
  Purchase #2 $100.43   6.255%   $106.7119   $106.71   $106.70   $106.70  
  Purchase #3 $58.93   5.285%   $62.0445   $62.04   $62.05   $62.00  
  Purchase #4 $11.42   6.535%   $12.1663   $12.17   $12.15   $12.20  
  Purchase #5 $68.80   12.475%   $77.3828   $77.38   $77.40   $77.40  
  Purchase #6 $112.94   10.336%   $124.6135   $124.61   $124.60   $124.60  
  Purchase #7 $31.40   3.250%   $32.4205   $32.42   $32.40   $32.40  
  7 purchase totals = $566.79       $612.0729   $612.06   $612.05   $612.00