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 $78.43   8.146%   $84.8189   $84.82   $84.80   $84.80  
  Purchase #2 $113.76   4.344%   $118.7017   $118.70   $118.70   $118.70  
  Purchase #3 $222.61   5.412%   $234.6577   $234.66   $234.65   $234.70  
  Purchase #4 $218.71   9.608%   $239.7237   $239.72   $239.70   $239.70  
  Purchase #5 $191.63   8.385%   $207.6982   $207.70   $207.70   $207.70  
  Purchase #6 $191.82   4.301%   $200.0702   $200.07   $200.05   $200.10  
  Purchase #7 $101.78   7.353%   $109.2639   $109.26   $109.25   $109.30  
  7 purchase totals = $1,118.74       $1,194.9343   $1,194.93   $1,194.85   $1,195.00