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 $148.70   3.267%   $153.558   $153.56   $153.55   $153.60  
  Purchase #2 $222.51   11.444%   $247.974   $247.97   $247.95   $248.00  
  Purchase #3 $142.47   11.471%   $158.8127   $158.81   $158.80   $158.80  
  Purchase #4 $45.79   8.533%   $49.6973   $49.70   $49.70   $49.70  
  Purchase #5 $56.49   3.214%   $58.3056   $58.31   $58.30   $58.30  
  Purchase #6 $32.40   6.554%   $34.5235   $34.52   $34.50   $34.50  
  Purchase #7 $84.25   9.691%   $92.4147   $92.41   $92.40   $92.40  
  7 purchase totals = $732.61       $795.2858   $795.28   $795.20   $795.30