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 $32.75   8.205%   $35.4371   $35.44   $35.45   $35.40  
  Purchase #2 $217.85   12.576%   $245.2468   $245.25   $245.25   $245.20  
  Purchase #3 $197.57   9.683%   $216.7007   $216.70   $216.70   $216.70  
  Purchase #4 $67.89   9.704%   $74.478   $74.48   $74.50   $74.50  
  Purchase #5 $55.25   7.245%   $59.2529   $59.25   $59.25   $59.30  
  Purchase #6 $151.93   10.807%   $168.3491   $168.35   $168.35   $168.30  
  Purchase #7 $207.92   11.844%   $232.546   $232.55   $232.55   $232.50  
  7 purchase totals = $931.16       $1,032.0106   $1,032.02   $1,032.05   $1,031.90