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 $106.99   6.325%   $113.7571   $113.76   $113.75   $113.80  
  Purchase #2 $213.38   7.157%   $228.6516   $228.65   $228.65   $228.70  
  Purchase #3 $210.58   7.166%   $225.6702   $225.67   $225.65   $225.70  
  Purchase #4 $44.69   6.422%   $47.56   $47.56   $47.55   $47.60  
  Purchase #5 $180.81   6.548%   $192.6494   $192.65   $192.65   $192.60  
  Purchase #6 $192.34   13.190%   $217.7096   $217.71   $217.70   $217.70  
  Purchase #7 $32.39   11.793%   $36.2098   $36.21   $36.20   $36.20  
  7 purchase totals = $981.18       $1,062.2077   $1,062.21   $1,062.15   $1,062.30