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 $64.53   7.822%   $69.5775   $69.58   $69.60   $69.60  
  Purchase #2 $73.80   4.598%   $77.1933   $77.19   $77.20   $77.20  
  Purchase #3 $153.79   9.576%   $168.5169   $168.52   $168.50   $168.50  
  Purchase #4 $184.31   4.538%   $192.674   $192.67   $192.65   $192.70  
  Purchase #5 $5.96   11.518%   $6.6465   $6.65   $6.65   $6.60  
  Purchase #6 $6.95   9.776%   $7.6294   $7.63   $7.65   $7.60  
  Purchase #7 $9.86   11.519%   $10.9958   $11.00   $11.00   $11.00  
  7 purchase totals = $499.20       $533.2334   $533.24   $533.25   $533.20