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 $78.52   5.385%   $82.7483   $82.75   $82.75   $82.70  
  Purchase #2 $227.42   3.711%   $235.8596   $235.86   $235.85   $235.90  
  Purchase #3 $151.29   10.790%   $167.6142   $167.61   $167.60   $167.60  
  Purchase #4 $47.66   4.297%   $49.708   $49.71   $49.70   $49.70  
  Purchase #5 $183.32   8.665%   $199.2047   $199.20   $199.20   $199.20  
  Purchase #6 $206.46   7.799%   $222.5618   $222.56   $222.55   $222.60  
  Purchase #7 $179.30   3.751%   $186.0255   $186.03   $186.05   $186.00  
  7 purchase totals = $1,073.97       $1,143.7221   $1,143.72   $1,143.70   $1,143.70