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 $101.68   10.117%   $111.967   $111.97   $111.95   $112.00  
  Purchase #2 $210.37   12.444%   $236.5484   $236.55   $236.55   $236.50  
  Purchase #3 $55.94   3.303%   $57.7877   $57.79   $57.80   $57.80  
  Purchase #4 $152.41   5.799%   $161.2483   $161.25   $161.25   $161.20  
  Purchase #5 $213.61   8.412%   $231.5789   $231.58   $231.60   $231.60  
  Purchase #6 $204.55   9.595%   $224.1766   $224.18   $224.20   $224.20  
  Purchase #7 $10.64   5.168%   $11.1899   $11.19   $11.20   $11.20  
  7 purchase totals = $949.20       $1,034.4968   $1,034.51   $1,034.55   $1,034.50