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 $174.88   12.450%   $196.6526   $196.65   $196.65   $196.70  
  Purchase #2 $205.97   4.718%   $215.6877   $215.69   $215.70   $215.70  
  Purchase #3 $130.83   3.234%   $135.061   $135.06   $135.05   $135.10  
  Purchase #4 $28.96   13.232%   $32.792   $32.79   $32.80   $32.80  
  Purchase #5 $34.46   4.819%   $36.1206   $36.12   $36.10   $36.10  
  Purchase #6 $205.73   10.628%   $227.595   $227.60   $227.60   $227.60  
  Purchase #7 $245.29   13.231%   $277.7443   $277.74   $277.75   $277.70  
  7 purchase totals = $1,026.12       $1,121.6532   $1,121.65   $1,121.65   $1,121.70