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 $96.72   11.485%   $107.8283   $107.83   $107.85   $107.80  
  Purchase #2 $196.39   5.529%   $207.2484   $207.25   $207.25   $207.20  
  Purchase #3 $234.86   6.863%   $250.9784   $250.98   $251.00   $251.00  
  Purchase #4 $69.90   11.244%   $77.7596   $77.76   $77.75   $77.80  
  Purchase #5 $233.28   11.722%   $260.6251   $260.63   $260.65   $260.60  
  Purchase #6 $155.99   6.366%   $165.9203   $165.92   $165.90   $165.90  
  Purchase #7 $147.68   9.809%   $162.1659   $162.17   $162.15   $162.20  
  7 purchase totals = $1,134.82       $1,232.5260   $1,232.54   $1,232.55   $1,232.50