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 $23.37   5.146%   $24.5726   $24.57   $24.55   $24.60  
  Purchase #2 $190.80   8.396%   $206.8196   $206.82   $206.80   $206.80  
  Purchase #3 $200.90   12.611%   $226.2355   $226.24   $226.25   $226.20  
  Purchase #4 $217.87   8.446%   $236.2713   $236.27   $236.25   $236.30  
  Purchase #5 $48.30   7.243%   $51.7984   $51.80   $51.80   $51.80  
  Purchase #6 $88.44   7.510%   $95.0818   $95.08   $95.10   $95.10  
  Purchase #7 $172.70   7.307%   $185.3192   $185.32   $185.30   $185.30  
  7 purchase totals = $942.38       $1,026.0984   $1,026.10   $1,026.05   $1,026.10