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 $82.98   13.674%   $94.3267   $94.33   $94.35   $94.30  
  Purchase #2 $38.72   10.716%   $42.8692   $42.87   $42.85   $42.90  
  Purchase #3 $32.74   5.592%   $34.5708   $34.57   $34.55   $34.60  
  Purchase #4 $57.82   6.790%   $61.746   $61.75   $61.75   $61.70  
  Purchase #5 $150.69   7.200%   $161.5397   $161.54   $161.55   $161.50  
  Purchase #6 $9.78   12.440%   $10.9966   $11.00   $11.00   $11.00  
  Purchase #7 $8.32   6.395%   $8.8521   $8.85   $8.85   $8.90  
  7 purchase totals = $381.05       $414.9011   $414.91   $414.90   $414.90