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 $84.59   13.426%   $95.9471   $95.95   $95.95   $95.90  
  Purchase #2 $223.55   10.179%   $246.3052   $246.31   $246.30   $246.30  
  Purchase #3 $126.52   6.843%   $135.1778   $135.18   $135.20   $135.20  
  Purchase #4 $207.82   13.248%   $235.352   $235.35   $235.35   $235.40  
  Purchase #5 $37.67   11.563%   $42.0258   $42.03   $42.05   $42.00  
  Purchase #6 $156.68   11.309%   $174.3989   $174.40   $174.40   $174.40  
  Purchase #7 $40.35   8.606%   $43.8225   $43.82   $43.80   $43.80  
  7 purchase totals = $877.18       $973.0293   $973.04   $973.05   $973.00