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 $90.71   5.113%   $95.348   $95.35   $95.35   $95.30  
  Purchase #2 $113.56   10.634%   $125.636   $125.64   $125.65   $125.60  
  Purchase #3 $137.82   8.633%   $149.718   $149.72   $149.70   $149.70  
  Purchase #4 $195.40   3.845%   $202.9131   $202.91   $202.90   $202.90  
  Purchase #5 $62.99   12.818%   $71.0641   $71.06   $71.05   $71.10  
  Purchase #6 $207.38   10.541%   $229.2399   $229.24   $229.25   $229.20  
  Purchase #7 $248.56   10.413%   $274.4426   $274.44   $274.45   $274.40  
  7 purchase totals = $1,056.42       $1,148.3617   $1,148.36   $1,148.35   $1,148.20