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 $214.31   9.163%   $233.9472   $233.95   $233.95   $233.90  
  Purchase #2 $61.56   5.304%   $64.8251   $64.83   $64.85   $64.80  
  Purchase #3 $47.67   10.867%   $52.8503   $52.85   $52.85   $52.90  
  Purchase #4 $132.30   13.354%   $149.9673   $149.97   $149.95   $150.00  
  Purchase #5 $212.83   3.704%   $220.7132   $220.71   $220.70   $220.70  
  Purchase #6 $115.72   9.315%   $126.4993   $126.50   $126.50   $126.50  
  Purchase #7 $201.55   13.174%   $228.1022   $228.10   $228.10   $228.10  
  7 purchase totals = $985.94       $1,076.9046   $1,076.91   $1,076.90   $1,076.90