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 $193.95   8.535%   $210.5036   $210.50   $210.50   $210.50  
  Purchase #2 $194.65   9.113%   $212.3885   $212.39   $212.40   $212.40  
  Purchase #3 $15.56   8.326%   $16.8555   $16.86   $16.85   $16.90  
  Purchase #4 $68.73   9.607%   $75.3329   $75.33   $75.35   $75.30  
  Purchase #5 $108.93   5.274%   $114.675   $114.68   $114.70   $114.70  
  Purchase #6 $10.26   11.605%   $11.4507   $11.45   $11.45   $11.50  
  Purchase #7 $168.90   9.776%   $185.4117   $185.41   $185.40   $185.40  
  7 purchase totals = $760.98       $826.6179   $826.62   $826.65   $826.70