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 $192.25   4.761%   $201.403   $201.40   $201.40   $201.40  
  Purchase #2 $101.82   12.866%   $114.9202   $114.92   $114.90   $114.90  
  Purchase #3 $24.86   12.498%   $27.967   $27.97   $27.95   $28.00  
  Purchase #4 $197.59   10.163%   $217.6711   $217.67   $217.65   $217.70  
  Purchase #5 $172.55   9.507%   $188.9543   $188.95   $188.95   $189.00  
  Purchase #6 $202.59   5.228%   $213.1814   $213.18   $213.20   $213.20  
  Purchase #7 $200.61   5.327%   $211.2965   $211.30   $211.30   $211.30  
  7 purchase totals = $1,092.27       $1,175.3935   $1,175.39   $1,175.35   $1,175.50