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 $208.57   9.764%   $228.9348   $228.93   $228.95   $228.90  
  Purchase #2 $201.41   5.727%   $212.9448   $212.94   $212.95   $212.90  
  Purchase #3 $41.30   11.369%   $45.9954   $46.00   $46.00   $46.00  
  Purchase #4 $220.52   7.233%   $236.4702   $236.47   $236.45   $236.50  
  Purchase #5 $9.89   7.500%   $10.6318   $10.63   $10.65   $10.60  
  Purchase #6 $238.75   6.483%   $254.2282   $254.23   $254.25   $254.20  
  Purchase #7 $152.40   11.750%   $170.307   $170.31   $170.30   $170.30  
  7 purchase totals = $1,072.84       $1,159.5122   $1,159.51   $1,159.55   $1,159.40