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 $87.62   8.720%   $95.2605   $95.26   $95.25   $95.30  
  Purchase #2 $144.97   13.722%   $164.8628   $164.86   $164.85   $164.90  
  Purchase #3 $182.90   6.808%   $195.3518   $195.35   $195.35   $195.40  
  Purchase #4 $186.52   12.449%   $209.7399   $209.74   $209.75   $209.70  
  Purchase #5 $46.37   5.469%   $48.906   $48.91   $48.90   $48.90  
  Purchase #6 $217.29   8.568%   $235.9074   $235.91   $235.90   $235.90  
  Purchase #7 $142.54   3.456%   $147.4662   $147.47   $147.45   $147.50  
  7 purchase totals = $1,008.21       $1,097.4946   $1,097.50   $1,097.45   $1,097.60