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 $201.90   5.213%   $212.425   $212.43   $212.45   $212.40  
  Purchase #2 $226.80   12.276%   $254.642   $254.64   $254.65   $254.60  
  Purchase #3 $92.36   5.867%   $97.7788   $97.78   $97.80   $97.80  
  Purchase #4 $83.58   7.861%   $90.1502   $90.15   $90.15   $90.20  
  Purchase #5 $56.85   5.688%   $60.0836   $60.08   $60.10   $60.10  
  Purchase #6 $45.34   13.423%   $51.426   $51.43   $51.45   $51.40  
  Purchase #7 $250.72   6.389%   $266.7385   $266.74   $266.75   $266.70  
  7 purchase totals = $957.55       $1,033.2441   $1,033.25   $1,033.35   $1,033.20