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 $67.39   10.722%   $74.6156   $74.62   $74.60   $74.60  
  Purchase #2 $10.73   10.647%   $11.8724   $11.87   $11.85   $11.90  
  Purchase #3 $249.54   12.234%   $280.0687   $280.07   $280.05   $280.10  
  Purchase #4 $60.55   9.747%   $66.4518   $66.45   $66.45   $66.50  
  Purchase #5 $176.58   11.751%   $197.3299   $197.33   $197.35   $197.30  
  Purchase #6 $212.34   7.371%   $227.9916   $227.99   $228.00   $228.00  
  Purchase #7 $195.45   4.851%   $204.9313   $204.93   $204.95   $204.90  
  7 purchase totals = $972.58       $1,063.2613   $1,063.26   $1,063.25   $1,063.30