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 $59.82   7.446%   $64.2742   $64.27   $64.25   $64.30  
  Purchase #2 $224.94   4.660%   $235.4222   $235.42   $235.40   $235.40  
  Purchase #3 $148.91   11.478%   $166.0019   $166.00   $166.00   $166.00  
  Purchase #4 $160.35   8.578%   $174.1048   $174.10   $174.10   $174.10  
  Purchase #5 $122.69   10.539%   $135.6203   $135.62   $135.60   $135.60  
  Purchase #6 $218.56   8.754%   $237.6927   $237.69   $237.70   $237.70  
  Purchase #7 $64.91   11.547%   $72.4052   $72.41   $72.40   $72.40  
  7 purchase totals = $1,000.18       $1,085.5213   $1,085.51   $1,085.45   $1,085.50