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 $217.49   4.404%   $227.0683   $227.07   $227.05   $227.10  
  Purchase #2 $150.99   10.580%   $166.9647   $166.96   $166.95   $167.00  
  Purchase #3 $237.92   3.126%   $245.3574   $245.36   $245.35   $245.40  
  Purchase #4 $207.67   6.821%   $221.8352   $221.84   $221.85   $221.80  
  Purchase #5 $178.50   10.112%   $196.5499   $196.55   $196.55   $196.50  
  Purchase #6 $245.52   9.327%   $268.4197   $268.42   $268.40   $268.40  
  Purchase #7 $17.78   12.840%   $20.063   $20.06   $20.05   $20.10  
  7 purchase totals = $1,255.87       $1,346.2582   $1,346.26   $1,346.20   $1,346.30