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 $73.58   13.757%   $83.7024   $83.70   $83.70   $83.70  
  Purchase #2 $182.56   8.290%   $197.6942   $197.69   $197.70   $197.70  
  Purchase #3 $206.62   3.364%   $213.5707   $213.57   $213.55   $213.60  
  Purchase #4 $177.31   5.464%   $186.9982   $187.00   $187.00   $187.00  
  Purchase #5 $12.51   11.592%   $13.9602   $13.96   $13.95   $14.00  
  Purchase #6 $25.30   6.800%   $27.0204   $27.02   $27.00   $27.00  
  Purchase #7 $231.89   5.465%   $244.5628   $244.56   $244.55   $244.60  
  7 purchase totals = $909.77       $967.5089   $967.50   $967.45   $967.60