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 $172.85   13.191%   $195.6506   $195.65   $195.65   $195.70  
  Purchase #2 $173.76   13.771%   $197.6885   $197.69   $197.70   $197.70  
  Purchase #3 $18.65   11.629%   $20.8188   $20.82   $20.80   $20.80  
  Purchase #4 $137.35   12.507%   $154.5284   $154.53   $154.55   $154.50  
  Purchase #5 $43.47   10.299%   $47.947   $47.95   $47.95   $47.90  
  Purchase #6 $147.97   8.399%   $160.398   $160.40   $160.40   $160.40  
  Purchase #7 $182.36   11.703%   $203.7016   $203.70   $203.70   $203.70  
  7 purchase totals = $876.41       $980.7329   $980.74   $980.75   $980.70