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 $117.44   7.462%   $126.2034   $126.20   $126.20   $126.20  
  Purchase #2 $121.81   13.519%   $138.2775   $138.28   $138.30   $138.30  
  Purchase #3 $15.80   11.541%   $17.6235   $17.62   $17.60   $17.60  
  Purchase #4 $169.70   7.521%   $182.4631   $182.46   $182.45   $182.50  
  Purchase #5 $151.99   12.688%   $171.2745   $171.27   $171.25   $171.30  
  Purchase #6 $187.85   12.146%   $210.6663   $210.67   $210.65   $210.70  
  Purchase #7 $209.54   11.868%   $234.4082   $234.41   $234.40   $234.40  
  7 purchase totals = $974.13       $1,080.9165   $1,080.91   $1,080.85   $1,081.00