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 $38.70   7.599%   $41.6408   $41.64   $41.65   $41.60  
  Purchase #2 $232.72   5.866%   $246.3714   $246.37   $246.35   $246.40  
  Purchase #3 $203.88   3.860%   $211.7498   $211.75   $211.75   $211.70  
  Purchase #4 $111.98   11.587%   $124.9551   $124.96   $124.95   $125.00  
  Purchase #5 $88.49   5.147%   $93.0446   $93.04   $93.05   $93.00  
  Purchase #6 $229.64   3.736%   $238.2194   $238.22   $238.20   $238.20  
  Purchase #7 $89.75   10.366%   $99.0535   $99.05   $99.05   $99.10  
  7 purchase totals = $995.16       $1,055.0346   $1,055.03   $1,055.00   $1,055.00