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 $61.25   10.504%   $67.6837   $67.68   $67.70   $67.70  
  Purchase #2 $170.54   10.371%   $188.2267   $188.23   $188.25   $188.20  
  Purchase #3 $87.61   12.415%   $98.4868   $98.49   $98.50   $98.50  
  Purchase #4 $183.79   7.324%   $197.2508   $197.25   $197.25   $197.30  
  Purchase #5 $238.34   3.847%   $247.5089   $247.51   $247.50   $247.50  
  Purchase #6 $236.75   6.291%   $251.6439   $251.64   $251.65   $251.60  
  Purchase #7 $219.94   10.454%   $242.9325   $242.93   $242.95   $242.90  
  7 purchase totals = $1,198.22       $1,293.7333   $1,293.73   $1,293.80   $1,293.70