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 $57.26   7.524%   $61.5682   $61.57   $61.55   $61.60  
  Purchase #2 $224.68   4.666%   $235.1636   $235.16   $235.15   $235.20  
  Purchase #3 $116.48   7.103%   $124.7536   $124.75   $124.75   $124.80  
  Purchase #4 $199.37   9.665%   $218.6391   $218.64   $218.65   $218.60  
  Purchase #5 $211.34   4.781%   $221.4442   $221.44   $221.45   $221.40  
  Purchase #6 $119.65   11.278%   $133.1441   $133.14   $133.15   $133.10  
  Purchase #7 $174.60   3.469%   $180.6569   $180.66   $180.65   $180.70  
  7 purchase totals = $1,103.38       $1,175.3697   $1,175.36   $1,175.35   $1,175.40