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 $41.97   3.444%   $43.4154   $43.42   $43.40   $43.40  
  Purchase #2 $235.97   13.422%   $267.6419   $267.64   $267.65   $267.60  
  Purchase #3 $59.94   12.281%   $67.3012   $67.30   $67.30   $67.30  
  Purchase #4 $56.36   13.156%   $63.7747   $63.77   $63.75   $63.80  
  Purchase #5 $88.67   7.750%   $95.5419   $95.54   $95.55   $95.50  
  Purchase #6 $218.49   10.671%   $241.8051   $241.81   $241.80   $241.80  
  Purchase #7 $250.78   9.628%   $274.9251   $274.93   $274.95   $274.90  
  7 purchase totals = $952.18       $1,054.4053   $1,054.41   $1,054.40   $1,054.30