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 $182.60   6.344%   $194.1841   $194.18   $194.20   $194.20  
  Purchase #2 $69.82   8.868%   $76.0116   $76.01   $76.00   $76.00  
  Purchase #3 $75.33   6.522%   $80.243   $80.24   $80.25   $80.20  
  Purchase #4 $88.99   8.124%   $96.2195   $96.22   $96.20   $96.20  
  Purchase #5 $200.51   3.432%   $207.3915   $207.39   $207.40   $207.40  
  Purchase #6 $249.58   3.643%   $258.6722   $258.67   $258.65   $258.70  
  Purchase #7 $149.79   4.122%   $155.9643   $155.96   $155.95   $156.00  
  7 purchase totals = $1,016.62       $1,068.6862   $1,068.67   $1,068.65   $1,068.70