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 $43.28   7.661%   $46.5957   $46.60   $46.60   $46.60  
  Purchase #2 $182.82   8.626%   $198.5901   $198.59   $198.60   $198.60  
  Purchase #3 $248.43   8.281%   $269.0025   $269.00   $269.00   $269.00  
  Purchase #4 $110.76   11.716%   $123.7366   $123.74   $123.75   $123.70  
  Purchase #5 $69.80   6.809%   $74.5527   $74.55   $74.55   $74.60  
  Purchase #6 $234.48   8.480%   $254.3639   $254.36   $254.35   $254.40  
  Purchase #7 $198.36   8.155%   $214.5363   $214.54   $214.55   $214.50  
  7 purchase totals = $1,087.93       $1,181.3778   $1,181.38   $1,181.40   $1,181.40