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 $168.79   8.321%   $182.835   $182.84   $182.85   $182.80  
  Purchase #2 $149.37   3.195%   $154.1424   $154.14   $154.15   $154.10  
  Purchase #3 $170.79   7.481%   $183.5668   $183.57   $183.55   $183.60  
  Purchase #4 $150.84   9.746%   $165.5409   $165.54   $165.55   $165.50  
  Purchase #5 $107.33   9.284%   $117.2945   $117.29   $117.30   $117.30  
  Purchase #6 $24.72   8.798%   $26.8949   $26.89   $26.90   $26.90  
  Purchase #7 $182.39   12.606%   $205.3821   $205.38   $205.40   $205.40  
  7 purchase totals = $954.23       $1,035.6566   $1,035.65   $1,035.70   $1,035.60