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 $225.39   9.601%   $247.0297   $247.03   $247.05   $247.00  
  Purchase #2 $210.64   10.423%   $232.595   $232.60   $232.60   $232.60  
  Purchase #3 $23.69   6.544%   $25.2403   $25.24   $25.25   $25.20  
  Purchase #4 $162.55   11.166%   $180.7003   $180.70   $180.70   $180.70  
  Purchase #5 $216.99   9.835%   $238.331   $238.33   $238.35   $238.30  
  Purchase #6 $38.82   6.260%   $41.2501   $41.25   $41.25   $41.30  
  Purchase #7 $169.96   11.588%   $189.655   $189.66   $189.65   $189.70  
  7 purchase totals = $1,048.04       $1,154.8014   $1,154.81   $1,154.85   $1,154.80