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 $49.27   13.171%   $55.7594   $55.76   $55.75   $55.80  
  Purchase #2 $24.41   6.865%   $26.0857   $26.09   $26.10   $26.10  
  Purchase #3 $41.87   9.827%   $45.9846   $45.98   $46.00   $46.00  
  Purchase #4 $177.56   9.107%   $193.7304   $193.73   $193.75   $193.70  
  Purchase #5 $214.69   13.622%   $243.9351   $243.94   $243.95   $243.90  
  Purchase #6 $246.88   3.741%   $256.1158   $256.12   $256.10   $256.10  
  Purchase #7 $199.65   13.416%   $226.435   $226.44   $226.45   $226.40  
  7 purchase totals = $954.33       $1,048.0460   $1,048.06   $1,048.10   $1,048.00