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 $208.51   5.144%   $219.2358   $219.24   $219.25   $219.20  
  Purchase #2 $200.48   13.382%   $227.3082   $227.31   $227.30   $227.30  
  Purchase #3 $77.56   9.506%   $84.9329   $84.93   $84.95   $84.90  
  Purchase #4 $162.55   7.309%   $174.4308   $174.43   $174.45   $174.40  
  Purchase #5 $24.91   6.832%   $26.6119   $26.61   $26.60   $26.60  
  Purchase #6 $50.42   8.762%   $54.8378   $54.84   $54.85   $54.80  
  Purchase #7 $226.43   9.354%   $247.6103   $247.61   $247.60   $247.60  
  7 purchase totals = $950.86       $1,034.9677   $1,034.97   $1,035.00   $1,034.80