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 $68.65   10.361%   $75.7628   $75.76   $75.75   $75.80  
  Purchase #2 $197.74   12.648%   $222.7502   $222.75   $222.75   $222.80  
  Purchase #3 $201.90   12.386%   $226.9073   $226.91   $226.90   $226.90  
  Purchase #4 $43.92   3.171%   $45.3127   $45.31   $45.30   $45.30  
  Purchase #5 $242.83   10.211%   $267.6254   $267.63   $267.65   $267.60  
  Purchase #6 $126.36   9.393%   $138.229   $138.23   $138.25   $138.20  
  Purchase #7 $174.54   8.236%   $188.9151   $188.92   $188.90   $188.90  
  7 purchase totals = $1,055.94       $1,165.5025   $1,165.51   $1,165.50   $1,165.50