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 $156.84   11.105%   $174.2571   $174.26   $174.25   $174.30  
  Purchase #2 $109.43   8.266%   $118.4755   $118.48   $118.50   $118.50  
  Purchase #3 $119.55   10.188%   $131.7298   $131.73   $131.75   $131.70  
  Purchase #4 $244.56   5.166%   $257.194   $257.19   $257.20   $257.20  
  Purchase #5 $148.57   4.724%   $155.5884   $155.59   $155.60   $155.60  
  Purchase #6 $202.79   11.227%   $225.5572   $225.56   $225.55   $225.60  
  Purchase #7 $137.94   10.176%   $151.9768   $151.98   $152.00   $152.00  
  7 purchase totals = $1,119.68       $1,214.7788   $1,214.79   $1,214.85   $1,214.90