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 $60.26   5.687%   $63.687   $63.69   $63.70   $63.70  
  Purchase #2 $111.98   5.240%   $117.8478   $117.85   $117.85   $117.80  
  Purchase #3 $21.42   5.415%   $22.5799   $22.58   $22.60   $22.60  
  Purchase #4 $57.94   9.748%   $63.588   $63.59   $63.60   $63.60  
  Purchase #5 $182.32   13.199%   $206.3844   $206.38   $206.40   $206.40  
  Purchase #6 $60.79   13.450%   $68.9663   $68.97   $68.95   $69.00  
  Purchase #7 $203.32   7.786%   $219.1505   $219.15   $219.15   $219.20  
  7 purchase totals = $698.03       $762.2039   $762.21   $762.25   $762.30