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 $189.76   3.159%   $195.7545   $195.75   $195.75   $195.80  
  Purchase #2 $174.35   12.202%   $195.6242   $195.62   $195.60   $195.60  
  Purchase #3 $100.88   11.181%   $112.1594   $112.16   $112.15   $112.20  
  Purchase #4 $65.50   6.864%   $69.9959   $70.00   $70.00   $70.00  
  Purchase #5 $74.64   7.347%   $80.1238   $80.12   $80.10   $80.10  
  Purchase #6 $234.82   7.636%   $252.7509   $252.75   $252.75   $252.80  
  Purchase #7 $95.78   12.854%   $108.0916   $108.09   $108.10   $108.10  
  7 purchase totals = $935.73       $1,014.5003   $1,014.49   $1,014.45   $1,014.60