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 $135.62   4.155%   $141.255   $141.26   $141.25   $141.30  
  Purchase #2 $228.53   6.242%   $242.7948   $242.79   $242.80   $242.80  
  Purchase #3 $133.95   4.864%   $140.4653   $140.47   $140.45   $140.50  
  Purchase #4 $50.71   3.601%   $52.5361   $52.54   $52.55   $52.50  
  Purchase #5 $197.62   6.566%   $210.5957   $210.60   $210.60   $210.60  
  Purchase #6 $166.27   11.768%   $185.8367   $185.84   $185.85   $185.80  
  Purchase #7 $110.35   10.135%   $121.534   $121.53   $121.55   $121.50  
  7 purchase totals = $1,023.05       $1,095.0176   $1,095.03   $1,095.05   $1,095.00