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 $69.27   11.132%   $76.9811   $76.98   $77.00   $77.00  
  Purchase #2 $122.96   13.552%   $139.6235   $139.62   $139.60   $139.60  
  Purchase #3 $181.87   10.526%   $201.0136   $201.01   $201.00   $201.00  
  Purchase #4 $67.62   10.635%   $74.8114   $74.81   $74.80   $74.80  
  Purchase #5 $45.52   12.433%   $51.1795   $51.18   $51.20   $51.20  
  Purchase #6 $197.58   4.338%   $206.151   $206.15   $206.15   $206.20  
  Purchase #7 $13.65   6.740%   $14.57   $14.57   $14.55   $14.60  
  7 purchase totals = $698.47       $764.3301   $764.32   $764.30   $764.40