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 $241.33   8.799%   $262.5646   $262.56   $262.55   $262.60  
  Purchase #2 $204.79   10.372%   $226.0308   $226.03   $226.05   $226.00  
  Purchase #3 $186.53   8.648%   $202.6611   $202.66   $202.65   $202.70  
  Purchase #4 $98.78   13.631%   $112.2447   $112.24   $112.25   $112.20  
  Purchase #5 $243.48   6.419%   $259.109   $259.11   $259.10   $259.10  
  Purchase #6 $65.59   3.623%   $67.9663   $67.97   $67.95   $68.00  
  Purchase #7 $228.55   4.349%   $238.4896   $238.49   $238.50   $238.50  
  7 purchase totals = $1,269.05       $1,369.0661   $1,369.06   $1,369.05   $1,369.10