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 $58.65   5.603%   $61.9362   $61.94   $61.95   $61.90  
  Purchase #2 $54.60   11.151%   $60.6884   $60.69   $60.70   $60.70  
  Purchase #3 $242.50   9.262%   $264.9604   $264.96   $264.95   $265.00  
  Purchase #4 $108.42   10.513%   $119.8182   $119.82   $119.80   $119.80  
  Purchase #5 $118.50   5.182%   $124.6407   $124.64   $124.65   $124.60  
  Purchase #6 $143.57   9.262%   $156.8675   $156.87   $156.85   $156.90  
  Purchase #7 $182.57   12.805%   $205.9481   $205.95   $205.95   $205.90  
  7 purchase totals = $908.81       $994.8595   $994.87   $994.85   $994.80