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 $184.29   11.554%   $205.5829   $205.58   $205.60   $205.60  
  Purchase #2 $104.92   10.178%   $115.5988   $115.60   $115.60   $115.60  
  Purchase #3 $43.64   5.137%   $45.8818   $45.88   $45.90   $45.90  
  Purchase #4 $132.96   11.639%   $148.4352   $148.44   $148.45   $148.40  
  Purchase #5 $119.61   13.810%   $136.1281   $136.13   $136.15   $136.10  
  Purchase #6 $186.45   9.815%   $204.7501   $204.75   $204.75   $204.80  
  Purchase #7 $242.64   8.396%   $263.0121   $263.01   $263.00   $263.00  
  7 purchase totals = $1,014.51       $1,119.3890   $1,119.39   $1,119.45   $1,119.40