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 $195.99   5.641%   $207.0458   $207.05   $207.05   $207.00  
  Purchase #2 $209.34   12.667%   $235.8571   $235.86   $235.85   $235.90  
  Purchase #3 $141.72   4.127%   $147.5688   $147.57   $147.55   $147.60  
  Purchase #4 $99.38   4.859%   $104.2089   $104.21   $104.20   $104.20  
  Purchase #5 $226.64   5.254%   $238.5477   $238.55   $238.55   $238.50  
  Purchase #6 $193.87   4.212%   $202.0358   $202.04   $202.05   $202.00  
  Purchase #7 $112.34   7.358%   $120.606   $120.61   $120.60   $120.60  
  7 purchase totals = $1,179.28       $1,255.8701   $1,255.89   $1,255.85   $1,255.80