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 $92.48   3.438%   $95.6595   $95.66   $95.65   $95.70  
  Purchase #2 $193.59   9.815%   $212.5909   $212.59   $212.60   $212.60  
  Purchase #3 $39.25   5.770%   $41.5147   $41.51   $41.50   $41.50  
  Purchase #4 $239.78   12.843%   $270.5749   $270.57   $270.55   $270.60  
  Purchase #5 $149.32   5.383%   $157.3579   $157.36   $157.35   $157.40  
  Purchase #6 $247.83   8.692%   $269.3714   $269.37   $269.35   $269.40  
  Purchase #7 $58.71   4.237%   $61.1975   $61.20   $61.20   $61.20  
  7 purchase totals = $1,020.96       $1,108.2668   $1,108.26   $1,108.20   $1,108.40