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 $119.98   4.436%   $125.3023   $125.30   $125.30   $125.30  
  Purchase #2 $90.33   13.658%   $102.6673   $102.67   $102.65   $102.70  
  Purchase #3 $87.49   8.514%   $94.9389   $94.94   $94.95   $94.90  
  Purchase #4 $150.49   12.759%   $169.691   $169.69   $169.70   $169.70  
  Purchase #5 $205.99   9.747%   $226.0678   $226.07   $226.05   $226.10  
  Purchase #6 $151.90   5.677%   $160.5234   $160.52   $160.50   $160.50  
  Purchase #7 $242.47   8.648%   $263.4388   $263.44   $263.45   $263.40  
  7 purchase totals = $1,048.65       $1,142.6295   $1,142.63   $1,142.60   $1,142.60