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 $91.37   4.726%   $95.6881   $95.69   $95.70   $95.70  
  Purchase #2 $52.44   3.836%   $54.4516   $54.45   $54.45   $54.50  
  Purchase #3 $144.96   11.591%   $161.7623   $161.76   $161.75   $161.80  
  Purchase #4 $173.86   8.118%   $187.974   $187.97   $187.95   $188.00  
  Purchase #5 $164.34   8.583%   $178.4453   $178.45   $178.45   $178.40  
  Purchase #6 $240.56   11.320%   $267.7914   $267.79   $267.80   $267.80  
  Purchase #7 $235.26   5.230%   $247.5641   $247.56   $247.55   $247.60  
  7 purchase totals = $1,102.79       $1,193.6768   $1,193.67   $1,193.65   $1,193.80