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 $84.97   12.233%   $95.3644   $95.36   $95.35   $95.40  
  Purchase #2 $98.82   6.452%   $105.1959   $105.20   $105.20   $105.20  
  Purchase #3 $179.52   11.386%   $199.9601   $199.96   $199.95   $200.00  
  Purchase #4 $200.40   3.466%   $207.3459   $207.35   $207.35   $207.30  
  Purchase #5 $25.84   10.553%   $28.5669   $28.57   $28.55   $28.60  
  Purchase #6 $188.56   7.507%   $202.7152   $202.72   $202.70   $202.70  
  Purchase #7 $103.72   4.538%   $108.4268   $108.43   $108.45   $108.40  
  7 purchase totals = $881.83       $947.5752   $947.59   $947.55   $947.60