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 $225.31   5.658%   $238.058   $238.06   $238.05   $238.10  
  Purchase #2 $232.64   3.755%   $241.3756   $241.38   $241.40   $241.40  
  Purchase #3 $154.46   8.808%   $168.0648   $168.06   $168.05   $168.10  
  Purchase #4 $241.65   5.648%   $255.2984   $255.30   $255.30   $255.30  
  Purchase #5 $188.32   7.517%   $202.476   $202.48   $202.50   $202.50  
  Purchase #6 $158.33   11.747%   $176.929   $176.93   $176.95   $176.90  
  Purchase #7 $75.96   5.324%   $80.0041   $80.00   $80.00   $80.00  
  7 purchase totals = $1,276.67       $1,362.2059   $1,362.21   $1,362.25   $1,362.30