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 $24.49   8.158%   $26.4879   $26.49   $26.50   $26.50  
  Purchase #2 $89.73   9.192%   $97.978   $97.98   $98.00   $98.00  
  Purchase #3 $201.96   8.677%   $219.4841   $219.48   $219.50   $219.50  
  Purchase #4 $211.80   11.642%   $236.4578   $236.46   $236.45   $236.50  
  Purchase #5 $210.76   7.276%   $226.0949   $226.09   $226.10   $226.10  
  Purchase #6 $63.52   7.835%   $68.4968   $68.50   $68.50   $68.50  
  Purchase #7 $205.70   12.670%   $231.7622   $231.76   $231.75   $231.80  
  7 purchase totals = $1,007.96       $1,106.7617   $1,106.76   $1,106.80   $1,106.90