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 $67.39   10.751%   $74.6351   $74.64   $74.65   $74.60  
  Purchase #2 $186.46   10.839%   $206.6704   $206.67   $206.65   $206.70  
  Purchase #3 $8.94   8.387%   $9.6898   $9.69   $9.70   $9.70  
  Purchase #4 $142.90   7.769%   $154.0019   $154.00   $154.00   $154.00  
  Purchase #5 $196.61   8.789%   $213.8901   $213.89   $213.90   $213.90  
  Purchase #6 $169.69   5.485%   $178.9975   $179.00   $179.00   $179.00  
  Purchase #7 $210.86   9.458%   $230.8031   $230.80   $230.80   $230.80  
  7 purchase totals = $982.85       $1,068.6879   $1,068.69   $1,068.70   $1,068.70