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 $212.76   11.177%   $236.5402   $236.54   $236.55   $236.50  
  Purchase #2 $31.51   12.145%   $35.3369   $35.34   $35.35   $35.30  
  Purchase #3 $169.29   13.833%   $192.7079   $192.71   $192.70   $192.70  
  Purchase #4 $127.82   7.603%   $137.5382   $137.54   $137.55   $137.50  
  Purchase #5 $198.82   8.580%   $215.8788   $215.88   $215.90   $215.90  
  Purchase #6 $82.86   4.190%   $86.3318   $86.33   $86.35   $86.30  
  Purchase #7 $189.83   6.598%   $202.355   $202.36   $202.35   $202.40  
  7 purchase totals = $1,012.89       $1,106.6888   $1,106.70   $1,106.75   $1,106.60