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 $56.49   10.504%   $62.4237   $62.42   $62.40   $62.40  
  Purchase #2 $231.53   13.418%   $262.5967   $262.60   $262.60   $262.60  
  Purchase #3 $201.33   12.334%   $226.162   $226.16   $226.15   $226.20  
  Purchase #4 $210.74   7.124%   $225.7531   $225.75   $225.75   $225.80  
  Purchase #5 $36.44   8.265%   $39.4518   $39.45   $39.45   $39.50  
  Purchase #6 $110.46   9.189%   $120.6102   $120.61   $120.60   $120.60  
  Purchase #7 $165.49   3.205%   $170.794   $170.79   $170.80   $170.80  
  7 purchase totals = $1,012.48       $1,107.7915   $1,107.78   $1,107.75   $1,107.90