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 $67.59   5.170%   $71.0844   $71.08   $71.10   $71.10  
  Purchase #2 $212.46   10.434%   $234.6281   $234.63   $234.65   $234.60  
  Purchase #3 $225.43   4.396%   $235.3399   $235.34   $235.35   $235.30  
  Purchase #4 $235.29   10.568%   $260.1554   $260.16   $260.15   $260.20  
  Purchase #5 $203.82   11.699%   $227.6649   $227.66   $227.65   $227.70  
  Purchase #6 $77.53   10.221%   $85.4543   $85.45   $85.45   $85.50  
  Purchase #7 $6.56   5.400%   $6.9142   $6.91   $6.90   $6.90  
  7 purchase totals = $1,028.68       $1,121.2412   $1,121.23   $1,121.25   $1,121.30