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 $61.75   12.668%   $69.5725   $69.57   $69.55   $69.60  
  Purchase #2 $190.28   6.605%   $202.848   $202.85   $202.85   $202.80  
  Purchase #3 $121.72   13.616%   $138.2934   $138.29   $138.30   $138.30  
  Purchase #4 $247.51   4.388%   $258.3707   $258.37   $258.35   $258.40  
  Purchase #5 $187.76   13.695%   $213.4737   $213.47   $213.45   $213.50  
  Purchase #6 $188.28   12.560%   $211.928   $211.93   $211.95   $211.90  
  Purchase #7 $99.70   7.442%   $107.1197   $107.12   $107.10   $107.10  
  7 purchase totals = $1,097.00       $1,201.6060   $1,201.60   $1,201.55   $1,201.60