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 $90.49   5.706%   $95.6534   $95.65   $95.65   $95.70  
  Purchase #2 $21.62   3.825%   $22.447   $22.45   $22.45   $22.40  
  Purchase #3 $96.92   11.144%   $107.7208   $107.72   $107.70   $107.70  
  Purchase #4 $63.76   5.366%   $67.1814   $67.18   $67.20   $67.20  
  Purchase #5 $201.98   4.514%   $211.0974   $211.10   $211.10   $211.10  
  Purchase #6 $15.79   5.419%   $16.6457   $16.65   $16.65   $16.60  
  Purchase #7 $216.96   4.295%   $226.2784   $226.28   $226.30   $226.30  
  7 purchase totals = $707.52       $747.0241   $747.03   $747.05   $747.00