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 $191.88   5.357%   $202.159   $202.16   $202.15   $202.20  
  Purchase #2 $58.48   9.447%   $64.0046   $64.00   $64.00   $64.00  
  Purchase #3 $155.55   12.126%   $174.412   $174.41   $174.40   $174.40  
  Purchase #4 $186.90   13.591%   $212.3016   $212.30   $212.30   $212.30  
  Purchase #5 $48.39   13.555%   $54.9493   $54.95   $54.95   $54.90  
  Purchase #6 $106.70   6.634%   $113.7785   $113.78   $113.80   $113.80  
  Purchase #7 $220.34   9.635%   $241.5698   $241.57   $241.55   $241.60  
  7 purchase totals = $968.24       $1,063.1748   $1,063.17   $1,063.15   $1,063.20