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 $194.71   5.413%   $205.2497   $205.25   $205.25   $205.20  
  Purchase #2 $71.50   7.308%   $76.7252   $76.73   $76.75   $76.70  
  Purchase #3 $211.60   5.303%   $222.8211   $222.82   $222.80   $222.80  
  Purchase #4 $118.72   3.311%   $122.6508   $122.65   $122.65   $122.70  
  Purchase #5 $12.54   4.111%   $13.0555   $13.06   $13.05   $13.10  
  Purchase #6 $75.37   3.294%   $77.8527   $77.85   $77.85   $77.90  
  Purchase #7 $58.89   7.734%   $63.4446   $63.44   $63.45   $63.40  
  7 purchase totals = $743.33       $781.7996   $781.80   $781.80   $781.80