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 $87.52   9.415%   $95.76   $95.76   $95.75   $95.80  
  Purchase #2 $136.79   5.780%   $144.6965   $144.70   $144.70   $144.70  
  Purchase #3 $161.62   13.371%   $183.2302   $183.23   $183.25   $183.20  
  Purchase #4 $152.87   9.627%   $167.5868   $167.59   $167.60   $167.60  
  Purchase #5 $23.51   5.857%   $24.887   $24.89   $24.90   $24.90  
  Purchase #6 $241.95   6.471%   $257.6066   $257.61   $257.60   $257.60  
  Purchase #7 $126.67   6.432%   $134.8174   $134.82   $134.80   $134.80  
  7 purchase totals = $930.93       $1,008.5845   $1,008.60   $1,008.60   $1,008.60