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 $191.27   10.702%   $211.7397   $211.74   $211.75   $211.70  
  Purchase #2 $110.53   3.122%   $113.9807   $113.98   $114.00   $114.00  
  Purchase #3 $250.89   5.248%   $264.0567   $264.06   $264.05   $264.10  
  Purchase #4 $139.95   8.438%   $151.759   $151.76   $151.75   $151.80  
  Purchase #5 $23.83   9.139%   $26.0078   $26.01   $26.00   $26.00  
  Purchase #6 $214.49   10.638%   $237.3074   $237.31   $237.30   $237.30  
  Purchase #7 $107.90   11.292%   $120.0841   $120.08   $120.10   $120.10  
  7 purchase totals = $1,038.86       $1,124.9354   $1,124.94   $1,124.95   $1,125.00