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 $33.69   9.623%   $36.932   $36.93   $36.95   $36.90  
  Purchase #2 $242.31   3.220%   $250.1124   $250.11   $250.10   $250.10  
  Purchase #3 $96.49   3.547%   $99.9125   $99.91   $99.90   $99.90  
  Purchase #4 $157.58   6.834%   $168.349   $168.35   $168.35   $168.30  
  Purchase #5 $26.55   3.592%   $27.5037   $27.50   $27.50   $27.50  
  Purchase #6 $168.71   7.817%   $181.8981   $181.90   $181.90   $181.90  
  Purchase #7 $156.48   11.222%   $174.0402   $174.04   $174.05   $174.00  
  7 purchase totals = $881.81       $938.7479   $938.74   $938.75   $938.60