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 $191.26   5.594%   $201.9591   $201.96   $201.95   $202.00  
  Purchase #2 $118.79   9.463%   $130.0311   $130.03   $130.05   $130.00  
  Purchase #3 $247.66   13.453%   $280.9777   $280.98   $281.00   $281.00  
  Purchase #4 $69.48   5.850%   $73.5446   $73.54   $73.55   $73.50  
  Purchase #5 $191.91   6.851%   $205.0578   $205.06   $205.05   $205.10  
  Purchase #6 $59.28   10.476%   $65.4902   $65.49   $65.50   $65.50  
  Purchase #7 $142.55   8.417%   $154.5484   $154.55   $154.55   $154.50  
  7 purchase totals = $1,020.93       $1,111.6089   $1,111.61   $1,111.65   $1,111.60