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 $58.65   3.565%   $60.7409   $60.74   $60.75   $60.70  
  Purchase #2 $211.29   12.569%   $237.847   $237.85   $237.85   $237.80  
  Purchase #3 $208.92   3.651%   $216.5477   $216.55   $216.55   $216.50  
  Purchase #4 $94.25   3.234%   $97.298   $97.30   $97.30   $97.30  
  Purchase #5 $83.66   9.590%   $91.683   $91.68   $91.70   $91.70  
  Purchase #6 $248.27   4.576%   $259.6308   $259.63   $259.65   $259.60  
  Purchase #7 $19.66   9.460%   $21.5198   $21.52   $21.50   $21.50  
  7 purchase totals = $924.70       $985.2672   $985.27   $985.30   $985.10