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 $93.36   13.540%   $106.0009   $106.00   $106.00   $106.00  
  Purchase #2 $188.29   10.126%   $207.3562   $207.36   $207.35   $207.40  
  Purchase #3 $14.93   12.304%   $16.767   $16.77   $16.75   $16.80  
  Purchase #4 $239.88   5.803%   $253.8002   $253.80   $253.80   $253.80  
  Purchase #5 $44.31   7.708%   $47.7254   $47.73   $47.75   $47.70  
  Purchase #6 $232.29   11.171%   $258.2391   $258.24   $258.25   $258.20  
  Purchase #7 $230.90   9.488%   $252.8078   $252.81   $252.80   $252.80  
  7 purchase totals = $1,043.96       $1,142.6966   $1,142.71   $1,142.70   $1,142.70