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 $204.52   11.416%   $227.868   $227.87   $227.85   $227.90  
  Purchase #2 $85.39   13.849%   $97.2157   $97.22   $97.20   $97.20  
  Purchase #3 $209.29   4.112%   $217.896   $217.90   $217.90   $217.90  
  Purchase #4 $51.71   13.336%   $58.606   $58.61   $58.60   $58.60  
  Purchase #5 $180.30   11.761%   $201.5051   $201.51   $201.50   $201.50  
  Purchase #6 $68.30   9.633%   $74.8793   $74.88   $74.90   $74.90  
  Purchase #7 $217.42   12.509%   $244.6171   $244.62   $244.60   $244.60  
  7 purchase totals = $1,016.93       $1,122.5872   $1,122.61   $1,122.55   $1,122.60