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 $98.35   10.754%   $108.9266   $108.93   $108.95   $108.90  
  Purchase #2 $206.65   8.646%   $224.517   $224.52   $224.50   $224.50  
  Purchase #3 $28.36   8.451%   $30.7567   $30.76   $30.75   $30.80  
  Purchase #4 $207.56   7.746%   $223.6376   $223.64   $223.65   $223.60  
  Purchase #5 $206.46   8.800%   $224.6285   $224.63   $224.65   $224.60  
  Purchase #6 $147.34   12.342%   $165.5247   $165.52   $165.50   $165.50  
  Purchase #7 $67.31   11.224%   $74.8649   $74.86   $74.85   $74.90  
  7 purchase totals = $962.03       $1,052.8560   $1,052.86   $1,052.85   $1,052.80