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 $23.49   11.709%   $26.2404   $26.24   $26.25   $26.20  
  Purchase #2 $130.46   12.660%   $146.9762   $146.98   $147.00   $147.00  
  Purchase #3 $78.46   9.401%   $85.836   $85.84   $85.85   $85.80  
  Purchase #4 $201.85   5.214%   $212.3745   $212.37   $212.35   $212.40  
  Purchase #5 $245.75   6.813%   $262.4929   $262.49   $262.50   $262.50  
  Purchase #6 $198.53   6.693%   $211.8176   $211.82   $211.80   $211.80  
  Purchase #7 $185.41   9.677%   $203.3521   $203.35   $203.35   $203.40  
  7 purchase totals = $1,063.95       $1,149.0897   $1,149.09   $1,149.10   $1,149.10