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 $213.79   10.516%   $236.2722   $236.27   $236.25   $236.30  
  Purchase #2 $55.43   12.180%   $62.1814   $62.18   $62.20   $62.20  
  Purchase #3 $153.50   9.129%   $167.513   $167.51   $167.50   $167.50  
  Purchase #4 $171.28   13.227%   $193.9352   $193.94   $193.95   $193.90  
  Purchase #5 $168.48   7.336%   $180.8397   $180.84   $180.85   $180.80  
  Purchase #6 $108.31   11.239%   $120.483   $120.48   $120.50   $120.50  
  Purchase #7 $230.81   5.186%   $242.7798   $242.78   $242.80   $242.80  
  7 purchase totals = $1,101.60       $1,204.0043   $1,204.00   $1,204.05   $1,204.00