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 $62.44   10.699%   $69.1205   $69.12   $69.10   $69.10  
  Purchase #2 $134.32   12.467%   $151.0657   $151.07   $151.05   $151.10  
  Purchase #3 $210.55   8.351%   $228.133   $228.13   $228.15   $228.10  
  Purchase #4 $169.27   8.442%   $183.5598   $183.56   $183.55   $183.60  
  Purchase #5 $229.82   6.867%   $245.6017   $245.60   $245.60   $245.60  
  Purchase #6 $82.96   3.156%   $85.5782   $85.58   $85.60   $85.60  
  Purchase #7 $155.41   5.398%   $163.799   $163.80   $163.80   $163.80  
  7 purchase totals = $1,044.77       $1,126.8579   $1,126.86   $1,126.85   $1,126.90