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 $92.70   11.747%   $103.5895   $103.59   $103.60   $103.60  
  Purchase #2 $23.54   9.772%   $25.8403   $25.84   $25.85   $25.80  
  Purchase #3 $185.90   3.345%   $192.1184   $192.12   $192.10   $192.10  
  Purchase #4 $240.67   5.841%   $254.7275   $254.73   $254.75   $254.70  
  Purchase #5 $14.92   6.571%   $15.9004   $15.90   $15.90   $15.90  
  Purchase #6 $162.69   5.675%   $171.9227   $171.92   $171.90   $171.90  
  Purchase #7 $246.62   6.228%   $261.9795   $261.98   $262.00   $262.00  
  7 purchase totals = $967.04       $1,026.0783   $1,026.08   $1,026.10   $1,026.00