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 $61.30   7.551%   $65.9288   $65.93   $65.95   $65.90  
  Purchase #2 $128.44   4.466%   $134.1761   $134.18   $134.20   $134.20  
  Purchase #3 $158.57   4.622%   $165.8991   $165.90   $165.90   $165.90  
  Purchase #4 $205.65   4.187%   $214.2606   $214.26   $214.25   $214.30  
  Purchase #5 $205.53   9.306%   $224.6566   $224.66   $224.65   $224.70  
  Purchase #6 $99.36   8.114%   $107.4221   $107.42   $107.40   $107.40  
  Purchase #7 $191.51   8.186%   $207.187   $207.19   $207.20   $207.20  
  7 purchase totals = $1,050.36       $1,119.5303   $1,119.54   $1,119.55   $1,119.60