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 $57.98   13.284%   $65.6821   $65.68   $65.70   $65.70  
  Purchase #2 $213.88   9.857%   $234.9622   $234.96   $234.95   $235.00  
  Purchase #3 $159.72   8.407%   $173.1477   $173.15   $173.15   $173.10  
  Purchase #4 $91.71   13.151%   $103.7708   $103.77   $103.75   $103.80  
  Purchase #5 $157.33   11.855%   $175.9815   $175.98   $176.00   $176.00  
  Purchase #6 $133.76   3.782%   $138.8188   $138.82   $138.80   $138.80  
  Purchase #7 $185.72   9.270%   $202.9362   $202.94   $202.95   $202.90  
  7 purchase totals = $1,000.10       $1,095.2993   $1,095.30   $1,095.30   $1,095.30