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 $32.81   5.344%   $34.5634   $34.56   $34.55   $34.60  
  Purchase #2 $49.25   9.619%   $53.9874   $53.99   $54.00   $54.00  
  Purchase #3 $55.91   5.581%   $59.0303   $59.03   $59.05   $59.00  
  Purchase #4 $201.62   5.155%   $212.0135   $212.01   $212.00   $212.00  
  Purchase #5 $246.26   4.682%   $257.7899   $257.79   $257.80   $257.80  
  Purchase #6 $202.77   11.158%   $225.3951   $225.40   $225.40   $225.40  
  Purchase #7 $179.67   5.704%   $189.9184   $189.92   $189.90   $189.90  
  7 purchase totals = $968.29       $1,032.6980   $1,032.70   $1,032.70   $1,032.70