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 $211.29   3.436%   $218.5499   $218.55   $218.55   $218.50  
  Purchase #2 $31.50   3.524%   $32.6101   $32.61   $32.60   $32.60  
  Purchase #3 $153.31   3.429%   $158.567   $158.57   $158.55   $158.60  
  Purchase #4 $231.81   5.687%   $244.993   $244.99   $245.00   $245.00  
  Purchase #5 $231.94   13.102%   $262.3288   $262.33   $262.35   $262.30  
  Purchase #6 $102.42   9.506%   $112.156   $112.16   $112.15   $112.20  
  Purchase #7 $158.93   4.282%   $165.7354   $165.74   $165.75   $165.70  
  7 purchase totals = $1,121.20       $1,194.9402   $1,194.95   $1,194.95   $1,194.90