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 $84.26   9.548%   $92.3051   $92.31   $92.30   $92.30  
  Purchase #2 $101.82   13.565%   $115.6319   $115.63   $115.65   $115.60  
  Purchase #3 $135.96   6.319%   $144.5513   $144.55   $144.55   $144.60  
  Purchase #4 $115.89   8.212%   $125.4069   $125.41   $125.40   $125.40  
  Purchase #5 $185.46   12.525%   $208.6889   $208.69   $208.70   $208.70  
  Purchase #6 $110.45   3.196%   $113.98   $113.98   $114.00   $114.00  
  Purchase #7 $236.52   3.333%   $244.4032   $244.40   $244.40   $244.40  
  7 purchase totals = $970.36       $1,044.9673   $1,044.97   $1,045.00   $1,045.00