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 $68.93   10.590%   $76.2297   $76.23   $76.25   $76.20  
  Purchase #2 $140.67   9.871%   $154.5555   $154.56   $154.55   $154.60  
  Purchase #3 $66.46   10.835%   $73.6609   $73.66   $73.65   $73.70  
  Purchase #4 $214.42   8.373%   $232.3734   $232.37   $232.35   $232.40  
  Purchase #5 $246.61   6.761%   $263.2833   $263.28   $263.30   $263.30  
  Purchase #6 $88.26   10.683%   $97.6888   $97.69   $97.70   $97.70  
  Purchase #7 $223.66   12.471%   $251.5526   $251.55   $251.55   $251.60  
  7 purchase totals = $1,049.01       $1,149.3442   $1,149.34   $1,149.35   $1,149.50