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 $212.36   13.498%   $241.0244   $241.02   $241.00   $241.00  
  Purchase #2 $169.28   3.645%   $175.4503   $175.45   $175.45   $175.50  
  Purchase #3 $207.38   3.282%   $214.1862   $214.19   $214.20   $214.20  
  Purchase #4 $185.55   4.663%   $194.2022   $194.20   $194.20   $194.20  
  Purchase #5 $133.97   6.565%   $142.7651   $142.77   $142.75   $142.80  
  Purchase #6 $80.51   13.490%   $91.3708   $91.37   $91.35   $91.40  
  Purchase #7 $131.83   8.702%   $143.3018   $143.30   $143.30   $143.30  
  7 purchase totals = $1,120.88       $1,202.3008   $1,202.30   $1,202.25   $1,202.40