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 $218.26   3.664%   $226.257   $226.26   $226.25   $226.30  
  Purchase #2 $191.66   11.799%   $214.274   $214.27   $214.25   $214.30  
  Purchase #3 $165.56   11.535%   $184.6573   $184.66   $184.65   $184.70  
  Purchase #4 $104.32   12.830%   $117.7043   $117.70   $117.70   $117.70  
  Purchase #5 $44.52   4.106%   $46.348   $46.35   $46.35   $46.30  
  Purchase #6 $220.72   11.296%   $245.6525   $245.65   $245.65   $245.70  
  Purchase #7 $11.92   3.158%   $12.2964   $12.30   $12.30   $12.30  
  7 purchase totals = $956.96       $1,047.1895   $1,047.19   $1,047.15   $1,047.30