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 $184.43   6.786%   $196.9454   $196.95   $196.95   $196.90  
  Purchase #2 $193.53   5.333%   $203.851   $203.85   $203.85   $203.90  
  Purchase #3 $123.36   7.795%   $132.9759   $132.98   $133.00   $133.00  
  Purchase #4 $145.49   5.774%   $153.8906   $153.89   $153.90   $153.90  
  Purchase #5 $148.33   5.860%   $157.0221   $157.02   $157.00   $157.00  
  Purchase #6 $221.34   4.152%   $230.53   $230.53   $230.55   $230.50  
  Purchase #7 $135.81   4.229%   $141.5534   $141.55   $141.55   $141.60  
  7 purchase totals = $1,152.29       $1,216.7684   $1,216.77   $1,216.80   $1,216.80