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 $194.79   3.701%   $201.9992   $202.00   $202.00   $202.00  
  Purchase #2 $31.43   8.385%   $34.0654   $34.07   $34.05   $34.10  
  Purchase #3 $40.62   9.478%   $44.47   $44.47   $44.45   $44.50  
  Purchase #4 $114.59   7.586%   $123.2828   $123.28   $123.30   $123.30  
  Purchase #5 $69.48   3.260%   $71.745   $71.75   $71.75   $71.70  
  Purchase #6 $205.39   10.419%   $226.7896   $226.79   $226.80   $226.80  
  Purchase #7 $97.75   3.467%   $101.139   $101.14   $101.15   $101.10  
  7 purchase totals = $754.05       $803.4910   $803.50   $803.50   $803.50