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 $59.48   9.265%   $64.9908   $64.99   $65.00   $65.00  
  Purchase #2 $41.32   12.659%   $46.5507   $46.55   $46.55   $46.60  
  Purchase #3 $244.29   12.825%   $275.6202   $275.62   $275.60   $275.60  
  Purchase #4 $231.77   13.531%   $263.1308   $263.13   $263.15   $263.10  
  Purchase #5 $182.26   12.674%   $205.3596   $205.36   $205.35   $205.40  
  Purchase #6 $96.72   3.169%   $99.7851   $99.79   $99.80   $99.80  
  Purchase #7 $184.25   11.581%   $205.588   $205.59   $205.60   $205.60  
  7 purchase totals = $1,040.09       $1,161.0252   $1,161.03   $1,161.05   $1,161.10