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 $90.53   12.663%   $101.9938   $101.99   $102.00   $102.00  
  Purchase #2 $195.51   3.124%   $201.6177   $201.62   $201.60   $201.60  
  Purchase #3 $125.47   5.203%   $131.9982   $132.00   $132.00   $132.00  
  Purchase #4 $150.25   3.164%   $155.0039   $155.00   $155.00   $155.00  
  Purchase #5 $56.99   8.625%   $61.9054   $61.91   $61.90   $61.90  
  Purchase #6 $113.70   13.382%   $128.9153   $128.92   $128.90   $128.90  
  Purchase #7 $165.81   9.304%   $181.237   $181.24   $181.25   $181.20  
  7 purchase totals = $898.26       $962.6713   $962.68   $962.65   $962.60