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 $95.93   5.857%   $101.5486   $101.55   $101.55   $101.50  
  Purchase #2 $207.30   10.557%   $229.1847   $229.18   $229.20   $229.20  
  Purchase #3 $211.39   11.276%   $235.2263   $235.23   $235.25   $235.20  
  Purchase #4 $237.43   13.148%   $268.6473   $268.65   $268.65   $268.60  
  Purchase #5 $202.59   8.441%   $219.6906   $219.69   $219.70   $219.70  
  Purchase #6 $145.45   9.383%   $159.0976   $159.10   $159.10   $159.10  
  Purchase #7 $229.84   8.750%   $249.951   $249.95   $249.95   $250.00  
  7 purchase totals = $1,329.93       $1,463.3461   $1,463.35   $1,463.40   $1,463.30