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 $88.58   6.812%   $94.6141   $94.61   $94.60   $94.60  
  Purchase #2 $244.92   5.346%   $258.0134   $258.01   $258.00   $258.00  
  Purchase #3 $221.60   7.267%   $237.7037   $237.70   $237.70   $237.70  
  Purchase #4 $79.88   5.802%   $84.5146   $84.51   $84.50   $84.50  
  Purchase #5 $212.64   8.370%   $230.438   $230.44   $230.45   $230.40  
  Purchase #6 $140.41   12.500%   $157.9613   $157.96   $157.95   $158.00  
  Purchase #7 $196.91   8.309%   $213.2713   $213.27   $213.25   $213.30  
  7 purchase totals = $1,184.94       $1,276.5164   $1,276.50   $1,276.45   $1,276.50