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 $110.27   8.532%   $119.6782   $119.68   $119.70   $119.70  
  Purchase #2 $142.67   10.601%   $157.7944   $157.79   $157.80   $157.80  
  Purchase #3 $119.87   7.491%   $128.8495   $128.85   $128.85   $128.80  
  Purchase #4 $54.30   5.568%   $57.3234   $57.32   $57.30   $57.30  
  Purchase #5 $212.88   6.475%   $226.664   $226.66   $226.65   $226.70  
  Purchase #6 $146.76   5.286%   $154.5177   $154.52   $154.50   $154.50  
  Purchase #7 $165.69   9.325%   $181.1406   $181.14   $181.15   $181.10  
  7 purchase totals = $952.44       $1,025.9678   $1,025.96   $1,025.95   $1,025.90