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 $216.26   11.683%   $241.5257   $241.53   $241.55   $241.50  
  Purchase #2 $167.25   4.403%   $174.614   $174.61   $174.60   $174.60  
  Purchase #3 $14.62   7.166%   $15.6677   $15.67   $15.65   $15.70  
  Purchase #4 $59.98   9.743%   $65.8239   $65.82   $65.80   $65.80  
  Purchase #5 $130.96   13.691%   $148.8897   $148.89   $148.90   $148.90  
  Purchase #6 $67.62   8.300%   $73.2325   $73.23   $73.25   $73.20  
  Purchase #7 $67.84   11.753%   $75.8132   $75.81   $75.80   $75.80  
  7 purchase totals = $724.53       $795.5667   $795.56   $795.55   $795.50