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 $87.54   5.594%   $92.437   $92.44   $92.45   $92.40  
  Purchase #2 $92.49   7.655%   $99.5701   $99.57   $99.55   $99.60  
  Purchase #3 $144.47   12.129%   $161.9928   $161.99   $162.00   $162.00  
  Purchase #4 $165.77   12.378%   $186.289   $186.29   $186.30   $186.30  
  Purchase #5 $216.65   12.410%   $243.5363   $243.54   $243.55   $243.50  
  Purchase #6 $203.76   10.124%   $224.3887   $224.39   $224.40   $224.40  
  Purchase #7 $248.49   4.289%   $259.1477   $259.15   $259.15   $259.10  
  7 purchase totals = $1,159.17       $1,267.3616   $1,267.37   $1,267.40   $1,267.30