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 $224.79   5.347%   $236.8095   $236.81   $236.80   $236.80  
  Purchase #2 $141.91   3.814%   $147.3224   $147.32   $147.30   $147.30  
  Purchase #3 $209.97   9.531%   $229.9822   $229.98   $230.00   $230.00  
  Purchase #4 $137.93   3.550%   $142.8265   $142.83   $142.85   $142.80  
  Purchase #5 $24.89   11.137%   $27.662   $27.66   $27.65   $27.70  
  Purchase #6 $61.73   6.118%   $65.5066   $65.51   $65.50   $65.50  
  Purchase #7 $41.67   7.146%   $44.6477   $44.65   $44.65   $44.60  
  7 purchase totals = $842.89       $894.7569   $894.76   $894.75   $894.70