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 $23.84   8.858%   $25.9517   $25.95   $25.95   $26.00  
  Purchase #2 $216.73   10.529%   $239.5495   $239.55   $239.55   $239.50  
  Purchase #3 $67.64   11.658%   $75.5255   $75.53   $75.55   $75.50  
  Purchase #4 $22.67   9.593%   $24.8447   $24.84   $24.85   $24.80  
  Purchase #5 $203.33   7.119%   $217.8051   $217.81   $217.80   $217.80  
  Purchase #6 $110.79   8.393%   $120.0886   $120.09   $120.10   $120.10  
  Purchase #7 $192.92   7.654%   $207.6861   $207.69   $207.70   $207.70  
  7 purchase totals = $837.92       $911.4512   $911.46   $911.50   $911.40