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 $89.61   4.506%   $93.6478   $93.65   $93.65   $93.60  
  Purchase #2 $48.76   5.189%   $51.2902   $51.29   $51.30   $51.30  
  Purchase #3 $25.62   3.503%   $26.5175   $26.52   $26.50   $26.50  
  Purchase #4 $205.68   13.777%   $234.0165   $234.02   $234.00   $234.00  
  Purchase #5 $68.54   4.806%   $71.834   $71.83   $71.85   $71.80  
  Purchase #6 $245.35   12.171%   $275.2115   $275.21   $275.20   $275.20  
  Purchase #7 $17.46   8.787%   $18.9942   $18.99   $19.00   $19.00  
  7 purchase totals = $701.02       $771.5117   $771.51   $771.50   $771.40