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 $60.46   13.848%   $68.8325   $68.83   $68.85   $68.80  
  Purchase #2 $155.45   3.574%   $161.0058   $161.01   $161.00   $161.00  
  Purchase #3 $177.62   12.165%   $199.2275   $199.23   $199.25   $199.20  
  Purchase #4 $97.83   13.413%   $110.9519   $110.95   $110.95   $111.00  
  Purchase #5 $233.67   8.559%   $253.6698   $253.67   $253.65   $253.70  
  Purchase #6 $136.75   9.624%   $149.9108   $149.91   $149.90   $149.90  
  Purchase #7 $172.68   7.492%   $185.6172   $185.62   $185.60   $185.60  
  7 purchase totals = $1,034.46       $1,129.2155   $1,129.22   $1,129.20   $1,129.20