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 $23.33   11.714%   $26.0629   $26.06   $26.05   $26.10  
  Purchase #2 $196.40   3.306%   $202.893   $202.89   $202.90   $202.90  
  Purchase #3 $219.82   3.163%   $226.7729   $226.77   $226.75   $226.80  
  Purchase #4 $150.97   3.530%   $156.2992   $156.30   $156.30   $156.30  
  Purchase #5 $30.94   5.427%   $32.6191   $32.62   $32.60   $32.60  
  Purchase #6 $100.51   3.521%   $104.049   $104.05   $104.05   $104.00  
  Purchase #7 $246.43   8.250%   $266.7605   $266.76   $266.75   $266.80  
  7 purchase totals = $968.40       $1,015.4566   $1,015.45   $1,015.40   $1,015.50