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 $197.73   3.816%   $205.2754   $205.28   $205.30   $205.30  
  Purchase #2 $147.35   13.781%   $167.6563   $167.66   $167.65   $167.70  
  Purchase #3 $9.50   12.590%   $10.6961   $10.70   $10.70   $10.70  
  Purchase #4 $190.57   12.184%   $213.789   $213.79   $213.80   $213.80  
  Purchase #5 $194.97   12.450%   $219.2438   $219.24   $219.25   $219.20  
  Purchase #6 $110.65   3.631%   $114.6677   $114.67   $114.65   $114.70  
  Purchase #7 $207.68   13.435%   $235.5818   $235.58   $235.60   $235.60  
  7 purchase totals = $1,058.45       $1,166.9101   $1,166.92   $1,166.95   $1,167.00