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 $244.27   6.151%   $259.295   $259.30   $259.30   $259.30  
  Purchase #2 $127.96   5.567%   $135.0835   $135.08   $135.10   $135.10  
  Purchase #3 $24.39   11.455%   $27.1839   $27.18   $27.20   $27.20  
  Purchase #4 $160.65   12.775%   $181.173   $181.17   $181.15   $181.20  
  Purchase #5 $118.40   5.798%   $125.2648   $125.26   $125.25   $125.30  
  Purchase #6 $231.78   9.759%   $254.3994   $254.40   $254.40   $254.40  
  Purchase #7 $112.64   6.771%   $120.2669   $120.27   $120.25   $120.30  
  7 purchase totals = $1,020.09       $1,102.6665   $1,102.66   $1,102.65   $1,102.80