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 $65.50   6.179%   $69.5472   $69.55   $69.55   $69.50  
  Purchase #2 $235.78   10.540%   $260.6312   $260.63   $260.65   $260.60  
  Purchase #3 $94.56   7.333%   $101.4941   $101.49   $101.50   $101.50  
  Purchase #4 $86.41   12.471%   $97.1862   $97.19   $97.20   $97.20  
  Purchase #5 $215.56   7.717%   $232.1948   $232.19   $232.20   $232.20  
  Purchase #6 $211.42   10.797%   $234.247   $234.25   $234.25   $234.20  
  Purchase #7 $198.52   6.436%   $211.2967   $211.30   $211.30   $211.30  
  7 purchase totals = $1,107.75       $1,206.5972   $1,206.60   $1,206.65   $1,206.50