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 $57.51   10.785%   $63.7125   $63.71   $63.70   $63.70  
  Purchase #2 $175.46   13.268%   $198.74   $198.74   $198.75   $198.70  
  Purchase #3 $27.79   5.399%   $29.2904   $29.29   $29.30   $29.30  
  Purchase #4 $202.46   12.564%   $227.8971   $227.90   $227.90   $227.90  
  Purchase #5 $133.46   13.746%   $151.8054   $151.81   $151.80   $151.80  
  Purchase #6 $169.72   3.466%   $175.6025   $175.60   $175.60   $175.60  
  Purchase #7 $106.66   12.756%   $120.2655   $120.27   $120.25   $120.30  
  7 purchase totals = $873.06       $967.3134   $967.32   $967.30   $967.30