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 $58.66   5.667%   $61.9843   $61.98   $62.00   $62.00  
  Purchase #2 $201.29   12.628%   $226.7089   $226.71   $226.70   $226.70  
  Purchase #3 $104.27   13.867%   $118.7291   $118.73   $118.75   $118.70  
  Purchase #4 $157.63   13.846%   $179.4554   $179.46   $179.45   $179.50  
  Purchase #5 $209.52   12.594%   $235.9069   $235.91   $235.90   $235.90  
  Purchase #6 $173.92   4.272%   $181.3499   $181.35   $181.35   $181.30  
  Purchase #7 $137.45   6.768%   $146.7526   $146.75   $146.75   $146.80  
  7 purchase totals = $1,042.74       $1,150.8871   $1,150.89   $1,150.90   $1,150.90