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 $41.35   4.751%   $43.3145   $43.31   $43.30   $43.30  
  Purchase #2 $79.59   6.757%   $84.9679   $84.97   $84.95   $85.00  
  Purchase #3 $157.48   8.528%   $170.9099   $170.91   $170.90   $170.90  
  Purchase #4 $245.63   12.110%   $275.3758   $275.38   $275.40   $275.40  
  Purchase #5 $78.55   4.230%   $81.8727   $81.87   $81.85   $81.90  
  Purchase #6 $211.46   3.241%   $218.3134   $218.31   $218.30   $218.30  
  Purchase #7 $182.56   9.649%   $200.1752   $200.18   $200.20   $200.20  
  7 purchase totals = $996.62       $1,074.9294   $1,074.93   $1,074.90   $1,075.00