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 $72.43   4.859%   $75.9494   $75.95   $75.95   $75.90  
  Purchase #2 $107.33   8.400%   $116.3457   $116.35   $116.35   $116.30  
  Purchase #3 $34.79   6.620%   $37.0931   $37.09   $37.10   $37.10  
  Purchase #4 $226.94   5.431%   $239.2651   $239.27   $239.25   $239.30  
  Purchase #5 $77.80   11.620%   $86.8404   $86.84   $86.85   $86.80  
  Purchase #6 $171.50   9.326%   $187.4941   $187.49   $187.50   $187.50  
  Purchase #7 $247.28   6.110%   $262.3888   $262.39   $262.40   $262.40  
  7 purchase totals = $938.07       $1,005.3766   $1,005.38   $1,005.40   $1,005.30