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 $184.26   4.803%   $193.11   $193.11   $193.10   $193.10  
  Purchase #2 $106.80   10.106%   $117.5932   $117.59   $117.60   $117.60  
  Purchase #3 $150.76   10.724%   $166.9275   $166.93   $166.95   $166.90  
  Purchase #4 $127.30   6.784%   $135.936   $135.94   $135.95   $135.90  
  Purchase #5 $115.79   5.337%   $121.9697   $121.97   $121.95   $122.00  
  Purchase #6 $50.64   10.387%   $55.9   $55.90   $55.90   $55.90  
  Purchase #7 $83.52   10.823%   $92.5594   $92.56   $92.55   $92.60  
  7 purchase totals = $819.07       $883.9958   $884.00   $884.00   $884.00