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 $56.42   4.730%   $59.0887   $59.09   $59.10   $59.10  
  Purchase #2 $211.43   10.336%   $233.2834   $233.28   $233.30   $233.30  
  Purchase #3 $207.34   3.107%   $213.7821   $213.78   $213.80   $213.80  
  Purchase #4 $68.66   12.840%   $77.4759   $77.48   $77.50   $77.50  
  Purchase #5 $202.70   3.827%   $210.4573   $210.46   $210.45   $210.50  
  Purchase #6 $214.50   6.678%   $228.8243   $228.82   $228.80   $228.80  
  Purchase #7 $181.64   5.587%   $191.7882   $191.79   $191.80   $191.80  
  7 purchase totals = $1,142.69       $1,214.6999   $1,214.70   $1,214.75   $1,214.80