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 $223.59   6.561%   $238.2597   $238.26   $238.25   $238.30  
  Purchase #2 $43.55   11.701%   $48.6458   $48.65   $48.65   $48.60  
  Purchase #3 $216.87   13.486%   $246.1171   $246.12   $246.10   $246.10  
  Purchase #4 $117.79   13.676%   $133.899   $133.90   $133.90   $133.90  
  Purchase #5 $95.81   6.438%   $101.9782   $101.98   $102.00   $102.00  
  Purchase #6 $118.56   4.563%   $123.9699   $123.97   $123.95   $124.00  
  Purchase #7 $124.51   5.859%   $131.805   $131.81   $131.80   $131.80  
  7 purchase totals = $940.68       $1,024.6747   $1,024.69   $1,024.65   $1,024.70