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 $71.61   3.538%   $74.1436   $74.14   $74.15   $74.10  
  Purchase #2 $82.46   3.727%   $85.5333   $85.53   $85.55   $85.50  
  Purchase #3 $146.39   3.408%   $151.379   $151.38   $151.40   $151.40  
  Purchase #4 $201.33   7.511%   $216.4519   $216.45   $216.45   $216.50  
  Purchase #5 $87.77   4.869%   $92.0435   $92.04   $92.05   $92.00  
  Purchase #6 $186.94   7.546%   $201.0465   $201.05   $201.05   $201.00  
  Purchase #7 $216.84   5.138%   $227.9812   $227.98   $228.00   $228.00  
  7 purchase totals = $993.34       $1,048.5790   $1,048.57   $1,048.65   $1,048.50