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 $195.93   13.166%   $221.7261   $221.73   $221.75   $221.70  
  Purchase #2 $54.66   7.346%   $58.6753   $58.68   $58.70   $58.70  
  Purchase #3 $141.46   5.684%   $149.5006   $149.50   $149.50   $149.50  
  Purchase #4 $5.58   4.501%   $5.8312   $5.83   $5.85   $5.80  
  Purchase #5 $21.52   8.109%   $23.2651   $23.27   $23.25   $23.30  
  Purchase #6 $108.60   13.442%   $123.198   $123.20   $123.20   $123.20  
  Purchase #7 $179.60   13.141%   $203.2012   $203.20   $203.20   $203.20  
  7 purchase totals = $707.35       $785.3975   $785.41   $785.45   $785.40