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 $212.80   5.728%   $224.9892   $224.99   $225.00   $225.00  
  Purchase #2 $229.91   4.566%   $240.4077   $240.41   $240.40   $240.40  
  Purchase #3 $198.71   5.351%   $209.343   $209.34   $209.35   $209.30  
  Purchase #4 $84.46   13.393%   $95.7717   $95.77   $95.75   $95.80  
  Purchase #5 $180.50   8.282%   $195.449   $195.45   $195.45   $195.40  
  Purchase #6 $107.42   9.372%   $117.4874   $117.49   $117.50   $117.50  
  Purchase #7 $45.48   4.178%   $47.3802   $47.38   $47.40   $47.40  
  7 purchase totals = $1,059.28       $1,130.8282   $1,130.83   $1,130.85   $1,130.80