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 $184.99   8.754%   $201.184   $201.18   $201.20   $201.20  
  Purchase #2 $124.32   9.396%   $136.0011   $136.00   $136.00   $136.00  
  Purchase #3 $171.98   12.200%   $192.9616   $192.96   $192.95   $193.00  
  Purchase #4 $217.38   3.571%   $225.1426   $225.14   $225.15   $225.10  
  Purchase #5 $23.38   5.471%   $24.6591   $24.66   $24.65   $24.70  
  Purchase #6 $197.91   5.305%   $208.4091   $208.41   $208.40   $208.40  
  Purchase #7 $170.62   4.767%   $178.7535   $178.75   $178.75   $178.80  
  7 purchase totals = $1,090.58       $1,167.1110   $1,167.10   $1,167.10   $1,167.20