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 $144.97   12.402%   $162.9492   $162.95   $162.95   $162.90  
  Purchase #2 $149.67   8.439%   $162.3007   $162.30   $162.30   $162.30  
  Purchase #3 $216.87   6.547%   $231.0685   $231.07   $231.05   $231.10  
  Purchase #4 $55.29   8.348%   $59.9056   $59.91   $59.90   $59.90  
  Purchase #5 $139.31   3.258%   $143.8487   $143.85   $143.85   $143.80  
  Purchase #6 $201.78   5.575%   $213.0292   $213.03   $213.05   $213.00  
  Purchase #7 $120.78   12.188%   $135.5007   $135.50   $135.50   $135.50  
  7 purchase totals = $1,028.67       $1,108.6026   $1,108.61   $1,108.60   $1,108.50