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 $232.34   5.221%   $244.4705   $244.47   $244.45   $244.50  
  Purchase #2 $108.62   6.543%   $115.727   $115.73   $115.75   $115.70  
  Purchase #3 $25.65   4.391%   $26.7763   $26.78   $26.80   $26.80  
  Purchase #4 $50.87   3.210%   $52.5029   $52.50   $52.50   $52.50  
  Purchase #5 $216.48   5.801%   $229.038   $229.04   $229.05   $229.00  
  Purchase #6 $214.53   9.619%   $235.1656   $235.17   $235.15   $235.20  
  Purchase #7 $181.83   10.654%   $201.2022   $201.20   $201.20   $201.20  
  7 purchase totals = $1,030.32       $1,104.8825   $1,104.89   $1,104.90   $1,104.90