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 $202.59   12.705%   $228.3291   $228.33   $228.35   $228.30  
  Purchase #2 $201.62   5.270%   $212.2454   $212.25   $212.25   $212.20  
  Purchase #3 $67.75   4.622%   $70.8814   $70.88   $70.90   $70.90  
  Purchase #4 $245.76   8.638%   $266.9887   $266.99   $267.00   $267.00  
  Purchase #5 $211.62   5.645%   $223.5659   $223.57   $223.55   $223.60  
  Purchase #6 $5.82   10.211%   $6.4143   $6.41   $6.40   $6.40  
  Purchase #7 $235.43   7.708%   $253.5769   $253.58   $253.60   $253.60  
  7 purchase totals = $1,170.59       $1,262.0017   $1,262.01   $1,262.05   $1,262.00