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 $201.46   6.244%   $214.0392   $214.04   $214.05   $214.00  
  Purchase #2 $190.61   10.121%   $209.9016   $209.90   $209.90   $209.90  
  Purchase #3 $172.56   3.253%   $178.1734   $178.17   $178.15   $178.20  
  Purchase #4 $31.67   3.443%   $32.7604   $32.76   $32.75   $32.80  
  Purchase #5 $203.93   12.261%   $228.9339   $228.93   $228.95   $228.90  
  Purchase #6 $239.64   12.394%   $269.341   $269.34   $269.35   $269.30  
  Purchase #7 $23.41   8.493%   $25.3982   $25.40   $25.40   $25.40  
  7 purchase totals = $1,063.28       $1,158.5477   $1,158.54   $1,158.55   $1,158.50