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 $209.65   11.460%   $233.6759   $233.68   $233.70   $233.70  
  Purchase #2 $141.40   3.253%   $145.9997   $146.00   $146.00   $146.00  
  Purchase #3 $206.73   4.486%   $216.0039   $216.00   $216.00   $216.00  
  Purchase #4 $185.75   8.751%   $202.005   $202.01   $202.00   $202.00  
  Purchase #5 $193.29   6.298%   $205.4634   $205.46   $205.45   $205.50  
  Purchase #6 $193.87   6.776%   $207.0066   $207.01   $207.00   $207.00  
  Purchase #7 $48.62   11.291%   $54.1097   $54.11   $54.10   $54.10  
  7 purchase totals = $1,179.31       $1,264.2642   $1,264.27   $1,264.25   $1,264.30