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 $194.25   11.518%   $216.6237   $216.62   $216.60   $216.60  
  Purchase #2 $188.39   5.236%   $198.2541   $198.25   $198.25   $198.30  
  Purchase #3 $131.81   3.207%   $136.0371   $136.04   $136.05   $136.00  
  Purchase #4 $192.40   10.597%   $212.7886   $212.79   $212.80   $212.80  
  Purchase #5 $244.53   6.630%   $260.7423   $260.74   $260.75   $260.70  
  Purchase #6 $204.93   12.406%   $230.3536   $230.35   $230.35   $230.40  
  Purchase #7 $210.66   4.546%   $220.2366   $220.24   $220.25   $220.20  
  7 purchase totals = $1,366.97       $1,475.0360   $1,475.03   $1,475.05   $1,475.00