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 $178.93   9.231%   $195.447   $195.45   $195.45   $195.40  
  Purchase #2 $70.55   6.708%   $75.2825   $75.28   $75.30   $75.30  
  Purchase #3 $16.78   4.551%   $17.5437   $17.54   $17.55   $17.50  
  Purchase #4 $147.61   13.213%   $167.1137   $167.11   $167.10   $167.10  
  Purchase #5 $181.35   6.624%   $193.3626   $193.36   $193.35   $193.40  
  Purchase #6 $171.82   4.507%   $179.5639   $179.56   $179.55   $179.60  
  Purchase #7 $249.59   9.566%   $273.4658   $273.47   $273.45   $273.50  
  7 purchase totals = $1,016.63       $1,101.7792   $1,101.77   $1,101.75   $1,101.80