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 $241.42   6.762%   $257.7448   $257.74   $257.75   $257.70  
  Purchase #2 $90.85   6.319%   $96.5908   $96.59   $96.60   $96.60  
  Purchase #3 $102.54   5.195%   $107.867   $107.87   $107.85   $107.90  
  Purchase #4 $205.77   7.705%   $221.6246   $221.62   $221.60   $221.60  
  Purchase #5 $173.35   3.835%   $179.998   $180.00   $180.00   $180.00  
  Purchase #6 $152.62   9.854%   $167.6592   $167.66   $167.65   $167.70  
  Purchase #7 $61.65   3.122%   $63.5747   $63.57   $63.55   $63.60  
  7 purchase totals = $1,028.20       $1,095.0591   $1,095.05   $1,095.00   $1,095.10