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   13.663%   $69.6186   $69.62   $69.60   $69.60  
  Purchase #2 $53.44   3.461%   $55.2896   $55.29   $55.30   $55.30  
  Purchase #3 $213.54   8.362%   $231.3962   $231.40   $231.40   $231.40  
  Purchase #4 $160.53   4.116%   $167.1374   $167.14   $167.15   $167.10  
  Purchase #5 $198.84   11.640%   $221.985   $221.99   $222.00   $222.00  
  Purchase #6 $8.29   13.605%   $9.4179   $9.42   $9.40   $9.40  
  Purchase #7 $51.36   9.685%   $56.3342   $56.33   $56.35   $56.30  
  7 purchase totals = $747.25       $811.1789   $811.19   $811.20   $811.10