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 $111.78   12.355%   $125.5904   $125.59   $125.60   $125.60  
  Purchase #2 $235.70   13.666%   $267.9108   $267.91   $267.90   $267.90  
  Purchase #3 $130.92   3.713%   $135.7811   $135.78   $135.80   $135.80  
  Purchase #4 $59.94   4.652%   $62.7284   $62.73   $62.75   $62.70  
  Purchase #5 $205.74   3.660%   $213.2701   $213.27   $213.25   $213.30  
  Purchase #6 $220.84   4.171%   $230.0512   $230.05   $230.05   $230.10  
  Purchase #7 $144.29   11.365%   $160.6886   $160.69   $160.70   $160.70  
  7 purchase totals = $1,109.21       $1,196.0206   $1,196.02   $1,196.05   $1,196.10