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 $69.36   10.590%   $76.7052   $76.71   $76.70   $76.70  
  Purchase #2 $187.93   7.868%   $202.7163   $202.72   $202.70   $202.70  
  Purchase #3 $149.80   12.562%   $168.6179   $168.62   $168.60   $168.60  
  Purchase #4 $123.33   13.302%   $139.7354   $139.74   $139.75   $139.70  
  Purchase #5 $55.32   7.657%   $59.5559   $59.56   $59.55   $59.60  
  Purchase #6 $181.76   5.792%   $192.2875   $192.29   $192.30   $192.30  
  Purchase #7 $92.69   5.542%   $97.8269   $97.83   $97.85   $97.80  
  7 purchase totals = $860.19       $937.4451   $937.47   $937.45   $937.40