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 $151.78   6.384%   $161.4696   $161.47   $161.45   $161.50  
  Purchase #2 $52.49   4.780%   $54.999   $55.00   $55.00   $55.00  
  Purchase #3 $250.49   6.405%   $266.5339   $266.53   $266.55   $266.50  
  Purchase #4 $161.25   11.704%   $180.1227   $180.12   $180.10   $180.10  
  Purchase #5 $13.46   6.533%   $14.3393   $14.34   $14.35   $14.30  
  Purchase #6 $208.57   6.118%   $221.3303   $221.33   $221.35   $221.30  
  Purchase #7 $186.84   5.430%   $196.9854   $196.99   $197.00   $197.00  
  7 purchase totals = $1,024.88       $1,095.7802   $1,095.78   $1,095.80   $1,095.70