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 $235.66   5.113%   $247.7093   $247.71   $247.70   $247.70  
  Purchase #2 $242.58   4.842%   $254.3257   $254.33   $254.35   $254.30  
  Purchase #3 $40.28   6.456%   $42.8805   $42.88   $42.90   $42.90  
  Purchase #4 $224.81   5.852%   $237.9659   $237.97   $237.95   $238.00  
  Purchase #5 $24.98   4.688%   $26.1511   $26.15   $26.15   $26.20  
  Purchase #6 $153.35   13.671%   $174.3145   $174.31   $174.30   $174.30  
  Purchase #7 $165.70   12.343%   $186.1524   $186.15   $186.15   $186.20  
  7 purchase totals = $1,087.36       $1,169.4994   $1,169.50   $1,169.50   $1,169.60