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 $118.93   4.820%   $124.6624   $124.66   $124.65   $124.70  
  Purchase #2 $231.85   11.475%   $258.4548   $258.45   $258.45   $258.50  
  Purchase #3 $26.42   11.289%   $29.4026   $29.40   $29.40   $29.40  
  Purchase #4 $231.62   4.614%   $242.3069   $242.31   $242.30   $242.30  
  Purchase #5 $162.67   10.367%   $179.534   $179.53   $179.55   $179.50  
  Purchase #6 $148.39   6.648%   $158.255   $158.26   $158.25   $158.30  
  Purchase #7 $31.37   4.377%   $32.7431   $32.74   $32.75   $32.70  
  7 purchase totals = $951.25       $1,025.3588   $1,025.35   $1,025.35   $1,025.40