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 $194.79   3.860%   $202.3089   $202.31   $202.30   $202.30  
  Purchase #2 $230.83   3.432%   $238.7521   $238.75   $238.75   $238.80  
  Purchase #3 $179.73   4.850%   $188.4469   $188.45   $188.45   $188.40  
  Purchase #4 $205.50   11.539%   $229.2126   $229.21   $229.20   $229.20  
  Purchase #5 $43.57   9.419%   $47.6739   $47.67   $47.65   $47.70  
  Purchase #6 $56.90   5.810%   $60.2059   $60.21   $60.20   $60.20  
  Purchase #7 $53.42   11.293%   $59.4527   $59.45   $59.45   $59.50  
  7 purchase totals = $964.74       $1,026.0530   $1,026.05   $1,026.00   $1,026.10