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 $110.61   3.380%   $114.3486   $114.35   $114.35   $114.30  
  Purchase #2 $191.86   3.147%   $197.8978   $197.90   $197.90   $197.90  
  Purchase #3 $209.26   4.257%   $218.1682   $218.17   $218.15   $218.20  
  Purchase #4 $71.93   3.208%   $74.2375   $74.24   $74.25   $74.20  
  Purchase #5 $11.52   5.537%   $12.1579   $12.16   $12.15   $12.20  
  Purchase #6 $205.47   13.262%   $232.7194   $232.72   $232.70   $232.70  
  Purchase #7 $22.91   3.230%   $23.65   $23.65   $23.65   $23.70  
  7 purchase totals = $823.56       $873.1794   $873.19   $873.15   $873.20