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 $115.74   9.517%   $126.755   $126.76   $126.75   $126.80  
  Purchase #2 $184.44   11.489%   $205.6303   $205.63   $205.65   $205.60  
  Purchase #3 $70.32   9.580%   $77.0567   $77.06   $77.05   $77.10  
  Purchase #4 $195.90   4.585%   $204.882   $204.88   $204.90   $204.90  
  Purchase #5 $239.62   3.104%   $247.0578   $247.06   $247.05   $247.10  
  Purchase #6 $181.85   13.451%   $206.3106   $206.31   $206.30   $206.30  
  Purchase #7 $143.65   5.818%   $152.0076   $152.01   $152.00   $152.00  
  7 purchase totals = $1,131.52       $1,219.7000   $1,219.71   $1,219.70   $1,219.80