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 $56.48   10.616%   $62.4759   $62.48   $62.50   $62.50  
  Purchase #2 $152.50   8.324%   $165.1941   $165.19   $165.20   $165.20  
  Purchase #3 $107.59   8.311%   $116.5318   $116.53   $116.55   $116.50  
  Purchase #4 $218.34   3.593%   $226.185   $226.19   $226.20   $226.20  
  Purchase #5 $207.74   4.679%   $217.4602   $217.46   $217.45   $217.50  
  Purchase #6 $205.25   7.585%   $220.8182   $220.82   $220.80   $220.80  
  Purchase #7 $168.26   7.462%   $180.8156   $180.82   $180.80   $180.80  
  7 purchase totals = $1,116.16       $1,189.4808   $1,189.49   $1,189.50   $1,189.50