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 $87.27   5.425%   $92.0044   $92.00   $92.00   $92.00  
  Purchase #2 $166.38   6.425%   $177.0699   $177.07   $177.05   $177.10  
  Purchase #3 $183.36   6.115%   $194.5725   $194.57   $194.55   $194.60  
  Purchase #4 $171.43   8.534%   $186.0598   $186.06   $186.05   $186.10  
  Purchase #5 $29.88   5.235%   $31.4442   $31.44   $31.45   $31.40  
  Purchase #6 $14.87   13.514%   $16.8795   $16.88   $16.90   $16.90  
  Purchase #7 $102.76   5.433%   $108.343   $108.34   $108.35   $108.30  
  7 purchase totals = $755.95       $806.3733   $806.36   $806.35   $806.40