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 $48.49   7.253%   $52.007   $52.01   $52.00   $52.00  
  Purchase #2 $213.38   10.510%   $235.8062   $235.81   $235.80   $235.80  
  Purchase #3 $64.65   9.749%   $70.9527   $70.95   $70.95   $71.00  
  Purchase #4 $147.57   4.671%   $154.463   $154.46   $154.45   $154.50  
  Purchase #5 $200.76   3.170%   $207.1241   $207.12   $207.10   $207.10  
  Purchase #6 $150.94   3.751%   $156.6018   $156.60   $156.60   $156.60  
  Purchase #7 $185.66   6.528%   $197.7799   $197.78   $197.80   $197.80  
  7 purchase totals = $1,011.45       $1,074.7347   $1,074.73   $1,074.70   $1,074.80