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 $191.68   4.417%   $200.1465   $200.15   $200.15   $200.10  
  Purchase #2 $96.51   13.216%   $109.2648   $109.26   $109.25   $109.30  
  Purchase #3 $172.69   7.609%   $185.83   $185.83   $185.85   $185.80  
  Purchase #4 $53.80   9.604%   $58.967   $58.97   $58.95   $59.00  
  Purchase #5 $127.76   8.373%   $138.4573   $138.46   $138.45   $138.50  
  Purchase #6 $191.84   13.502%   $217.7422   $217.74   $217.75   $217.70  
  Purchase #7 $196.76   3.267%   $203.1881   $203.19   $203.20   $203.20  
  7 purchase totals = $1,031.04       $1,113.5959   $1,113.60   $1,113.60   $1,113.60