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 $43.61   13.639%   $49.558   $49.56   $49.55   $49.60  
  Purchase #2 $162.27   7.291%   $174.1011   $174.10   $174.10   $174.10  
  Purchase #3 $56.31   11.644%   $62.8667   $62.87   $62.85   $62.90  
  Purchase #4 $192.51   13.107%   $217.7423   $217.74   $217.75   $217.70  
  Purchase #5 $216.84   13.170%   $245.3978   $245.40   $245.40   $245.40  
  Purchase #6 $203.58   12.812%   $229.6627   $229.66   $229.65   $229.70  
  Purchase #7 $31.51   10.446%   $34.8015   $34.80   $34.80   $34.80  
  7 purchase totals = $906.63       $1,014.1301   $1,014.13   $1,014.10   $1,014.20