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 $126.58   6.280%   $134.5292   $134.53   $134.55   $134.50  
  Purchase #2 $207.48   6.542%   $221.0533   $221.05   $221.05   $221.10  
  Purchase #3 $232.25   10.181%   $255.8954   $255.90   $255.90   $255.90  
  Purchase #4 $170.54   6.842%   $182.2083   $182.21   $182.20   $182.20  
  Purchase #5 $97.29   5.449%   $102.5913   $102.59   $102.60   $102.60  
  Purchase #6 $140.59   8.677%   $152.789   $152.79   $152.80   $152.80  
  Purchase #7 $96.66   8.190%   $104.5765   $104.58   $104.60   $104.60  
  7 purchase totals = $1,071.39       $1,153.6430   $1,153.65   $1,153.70   $1,153.70