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 $67.90   9.783%   $74.5427   $74.54   $74.55   $74.50  
  Purchase #2 $108.99   7.806%   $117.4978   $117.50   $117.50   $117.50  
  Purchase #3 $118.65   12.411%   $133.3757   $133.38   $133.40   $133.40  
  Purchase #4 $88.57   8.741%   $96.3119   $96.31   $96.30   $96.30  
  Purchase #5 $102.70   4.598%   $107.4221   $107.42   $107.40   $107.40  
  Purchase #6 $201.72   6.346%   $214.5212   $214.52   $214.50   $214.50  
  Purchase #7 $15.52   5.291%   $16.3412   $16.34   $16.35   $16.30  
  7 purchase totals = $704.05       $760.0126   $760.01   $760.00   $759.90