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 $87.39   8.722%   $95.0122   $95.01   $95.00   $95.00  
  Purchase #2 $225.28   12.613%   $253.6946   $253.69   $253.70   $253.70  
  Purchase #3 $189.74   6.586%   $202.2363   $202.24   $202.25   $202.20  
  Purchase #4 $154.75   4.722%   $162.0573   $162.06   $162.05   $162.10  
  Purchase #5 $145.60   5.517%   $153.6328   $153.63   $153.65   $153.60  
  Purchase #6 $34.32   13.239%   $38.8636   $38.86   $38.85   $38.90  
  Purchase #7 $87.54   6.754%   $93.4525   $93.45   $93.45   $93.50  
  7 purchase totals = $924.62       $998.9493   $998.94   $998.95   $999.00