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 $164.66   5.679%   $174.011   $174.01   $174.00   $174.00  
  Purchase #2 $44.44   11.858%   $49.7097   $49.71   $49.70   $49.70  
  Purchase #3 $42.82   9.167%   $46.7453   $46.75   $46.75   $46.70  
  Purchase #4 $53.33   3.785%   $55.3485   $55.35   $55.35   $55.30  
  Purchase #5 $193.78   5.142%   $203.7442   $203.74   $203.75   $203.70  
  Purchase #6 $201.42   11.625%   $224.8351   $224.84   $224.85   $224.80  
  Purchase #7 $242.36   4.209%   $252.5609   $252.56   $252.55   $252.60  
  7 purchase totals = $942.81       $1,006.9547   $1,006.96   $1,006.95   $1,006.80