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 $87.61   10.428%   $96.746   $96.75   $96.75   $96.70  
  Purchase #2 $202.94   10.676%   $224.6059   $224.61   $224.60   $224.60  
  Purchase #3 $236.89   13.507%   $268.8867   $268.89   $268.90   $268.90  
  Purchase #4 $23.64   3.649%   $24.5026   $24.50   $24.50   $24.50  
  Purchase #5 $27.42   12.509%   $30.85   $30.85   $30.85   $30.90  
  Purchase #6 $77.59   10.390%   $85.6516   $85.65   $85.65   $85.70  
  Purchase #7 $66.74   10.598%   $73.8131   $73.81   $73.80   $73.80  
  7 purchase totals = $722.83       $805.0559   $805.06   $805.05   $805.10