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 $227.65   7.627%   $245.0129   $245.01   $245.00   $245.00  
  Purchase #2 $90.60   8.135%   $97.9703   $97.97   $97.95   $98.00  
  Purchase #3 $102.88   12.421%   $115.6587   $115.66   $115.65   $115.70  
  Purchase #4 $161.91   9.487%   $177.2704   $177.27   $177.25   $177.30  
  Purchase #5 $37.27   3.827%   $38.6963   $38.70   $38.70   $38.70  
  Purchase #6 $189.79   8.402%   $205.7362   $205.74   $205.75   $205.70  
  Purchase #7 $129.68   3.495%   $134.2123   $134.21   $134.20   $134.20  
  7 purchase totals = $939.78       $1,014.5571   $1,014.56   $1,014.50   $1,014.60