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 $84.95   12.732%   $95.7658   $95.77   $95.75   $95.80  
  Purchase #2 $162.59   12.861%   $183.5007   $183.50   $183.50   $183.50  
  Purchase #3 $203.64   13.485%   $231.1009   $231.10   $231.10   $231.10  
  Purchase #4 $248.40   7.819%   $267.8224   $267.82   $267.80   $267.80  
  Purchase #5 $192.75   7.444%   $207.0983   $207.10   $207.10   $207.10  
  Purchase #6 $222.85   5.182%   $234.3981   $234.40   $234.40   $234.40  
  Purchase #7 $59.45   6.598%   $63.3725   $63.37   $63.35   $63.40  
  7 purchase totals = $1,174.63       $1,283.0587   $1,283.06   $1,283.00   $1,283.10