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 $24.66   5.529%   $26.0235   $26.02   $26.00   $26.00  
  Purchase #2 $137.67   8.720%   $149.6748   $149.67   $149.65   $149.70  
  Purchase #3 $155.42   4.428%   $162.302   $162.30   $162.30   $162.30  
  Purchase #4 $167.87   12.106%   $188.1923   $188.19   $188.20   $188.20  
  Purchase #5 $246.82   9.748%   $270.88   $270.88   $270.90   $270.90  
  Purchase #6 $67.76   10.481%   $74.8619   $74.86   $74.85   $74.90  
  Purchase #7 $216.94   11.644%   $242.2005   $242.20   $242.20   $242.20  
  7 purchase totals = $1,017.14       $1,114.1350   $1,114.12   $1,114.10   $1,114.20