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 $67.58   13.480%   $76.6898   $76.69   $76.70   $76.70  
  Purchase #2 $189.32   8.263%   $204.9635   $204.96   $204.95   $205.00  
  Purchase #3 $250.73   9.595%   $274.7875   $274.79   $274.80   $274.80  
  Purchase #4 $95.51   7.354%   $102.5338   $102.53   $102.55   $102.50  
  Purchase #5 $171.54   13.335%   $194.4149   $194.41   $194.40   $194.40  
  Purchase #6 $11.86   3.592%   $12.286   $12.29   $12.30   $12.30  
  Purchase #7 $215.54   6.129%   $228.7504   $228.75   $228.75   $228.80  
  7 purchase totals = $1,002.08       $1,094.4259   $1,094.42   $1,094.45   $1,094.50