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 $88.44   7.814%   $95.3507   $95.35   $95.35   $95.40  
  Purchase #2 $76.61   4.676%   $80.1923   $80.19   $80.20   $80.20  
  Purchase #3 $98.97   8.339%   $107.2231   $107.22   $107.20   $107.20  
  Purchase #4 $164.78   11.318%   $183.4298   $183.43   $183.45   $183.40  
  Purchase #5 $223.53   5.236%   $235.234   $235.23   $235.25   $235.20  
  Purchase #6 $224.54   7.722%   $241.879   $241.88   $241.90   $241.90  
  Purchase #7 $71.59   6.778%   $76.4424   $76.44   $76.45   $76.40  
  7 purchase totals = $948.46       $1,019.7513   $1,019.74   $1,019.80   $1,019.70