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 $22.84   12.180%   $25.6219   $25.62   $25.60   $25.60  
  Purchase #2 $162.56   11.518%   $181.2837   $181.28   $181.30   $181.30  
  Purchase #3 $83.60   4.157%   $87.0753   $87.08   $87.10   $87.10  
  Purchase #4 $188.71   4.126%   $196.4962   $196.50   $196.50   $196.50  
  Purchase #5 $57.70   5.812%   $61.0535   $61.05   $61.05   $61.10  
  Purchase #6 $21.37   8.470%   $23.18   $23.18   $23.20   $23.20  
  Purchase #7 $167.88   11.173%   $186.6372   $186.64   $186.65   $186.60  
  7 purchase totals = $704.66       $761.3478   $761.35   $761.40   $761.40