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 $69.34   6.590%   $73.9095   $73.91   $73.90   $73.90  
  Purchase #2 $201.59   6.572%   $214.8385   $214.84   $214.85   $214.80  
  Purchase #3 $216.83   11.349%   $241.438   $241.44   $241.45   $241.40  
  Purchase #4 $57.95   9.835%   $63.6494   $63.65   $63.65   $63.60  
  Purchase #5 $192.87   11.758%   $215.5477   $215.55   $215.55   $215.50  
  Purchase #6 $240.72   4.838%   $252.366   $252.37   $252.35   $252.40  
  Purchase #7 $187.43   8.792%   $203.9088   $203.91   $203.90   $203.90  
  7 purchase totals = $1,166.73       $1,265.6579   $1,265.67   $1,265.65   $1,265.50