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 $236.71   7.189%   $253.7271   $253.73   $253.75   $253.70  
  Purchase #2 $180.41   3.836%   $187.3305   $187.33   $187.35   $187.30  
  Purchase #3 $198.49   3.417%   $205.2724   $205.27   $205.25   $205.30  
  Purchase #4 $189.98   12.651%   $214.0144   $214.01   $214.00   $214.00  
  Purchase #5 $56.93   3.172%   $58.7358   $58.74   $58.75   $58.70  
  Purchase #6 $41.38   6.544%   $44.0879   $44.09   $44.10   $44.10  
  Purchase #7 $154.70   5.304%   $162.9053   $162.91   $162.90   $162.90  
  7 purchase totals = $1,058.60       $1,126.0734   $1,126.08   $1,126.10   $1,126.00