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 $85.39   12.653%   $96.1944   $96.19   $96.20   $96.20  
  Purchase #2 $185.85   10.608%   $205.565   $205.57   $205.55   $205.60  
  Purchase #3 $71.59   4.244%   $74.6283   $74.63   $74.65   $74.60  
  Purchase #4 $203.55   6.543%   $216.8683   $216.87   $216.85   $216.90  
  Purchase #5 $143.92   5.835%   $152.3177   $152.32   $152.30   $152.30  
  Purchase #6 $197.76   3.152%   $203.9934   $203.99   $204.00   $204.00  
  Purchase #7 $231.92   13.777%   $263.8716   $263.87   $263.85   $263.90  
  7 purchase totals = $1,119.98       $1,213.4387   $1,213.44   $1,213.40   $1,213.50