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 $84.81   12.431%   $95.3527   $95.35   $95.35   $95.40  
  Purchase #2 $184.65   8.852%   $200.9952   $201.00   $201.00   $201.00  
  Purchase #3 $189.96   6.814%   $202.9039   $202.90   $202.90   $202.90  
  Purchase #4 $212.42   10.630%   $235.0002   $235.00   $235.00   $235.00  
  Purchase #5 $140.79   10.452%   $155.5054   $155.51   $155.50   $155.50  
  Purchase #6 $167.86   13.362%   $190.2895   $190.29   $190.30   $190.30  
  Purchase #7 $248.81   3.794%   $258.2499   $258.25   $258.25   $258.20  
  7 purchase totals = $1,229.30       $1,338.2968   $1,338.30   $1,338.30   $1,338.30