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 $208.72   5.816%   $220.8592   $220.86   $220.85   $220.90  
  Purchase #2 $155.55   10.438%   $171.7863   $171.79   $171.80   $171.80  
  Purchase #3 $234.60   4.249%   $244.5682   $244.57   $244.55   $244.60  
  Purchase #4 $73.67   5.206%   $77.5053   $77.51   $77.50   $77.50  
  Purchase #5 $215.83   7.184%   $231.3352   $231.34   $231.35   $231.30  
  Purchase #6 $28.46   4.111%   $29.63   $29.63   $29.65   $29.60  
  Purchase #7 $46.26   4.244%   $48.2233   $48.22   $48.20   $48.20  
  7 purchase totals = $963.09       $1,023.9075   $1,023.92   $1,023.90   $1,023.90