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 $87.88   6.593%   $93.6739   $93.67   $93.65   $93.70  
  Purchase #2 $218.28   11.438%   $243.2469   $243.25   $243.25   $243.20  
  Purchase #3 $197.88   5.119%   $208.0095   $208.01   $208.00   $208.00  
  Purchase #4 $151.39   4.807%   $158.6673   $158.67   $158.65   $158.70  
  Purchase #5 $190.63   11.753%   $213.0347   $213.03   $213.05   $213.00  
  Purchase #6 $26.93   6.709%   $28.7367   $28.74   $28.75   $28.70  
  Purchase #7 $162.55   11.522%   $181.279   $181.28   $181.30   $181.30  
  7 purchase totals = $1,035.54       $1,126.6480   $1,126.65   $1,126.65   $1,126.60