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 $184.48   11.627%   $205.9295   $205.93   $205.95   $205.90  
  Purchase #2 $99.42   6.199%   $105.583   $105.58   $105.60   $105.60  
  Purchase #3 $93.70   13.541%   $106.3879   $106.39   $106.40   $106.40  
  Purchase #4 $239.43   7.626%   $257.6889   $257.69   $257.70   $257.70  
  Purchase #5 $76.73   6.144%   $81.4443   $81.44   $81.45   $81.40  
  Purchase #6 $141.28   5.588%   $149.1747   $149.17   $149.15   $149.20  
  Purchase #7 $240.98   4.168%   $251.024   $251.02   $251.00   $251.00  
  7 purchase totals = $1,076.02       $1,157.2323   $1,157.22   $1,157.25   $1,157.20