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 $108.78   5.673%   $114.9511   $114.95   $114.95   $115.00  
  Purchase #2 $228.41   5.162%   $240.2005   $240.20   $240.20   $240.20  
  Purchase #3 $15.58   6.737%   $16.6296   $16.63   $16.65   $16.60  
  Purchase #4 $55.35   7.538%   $59.5223   $59.52   $59.50   $59.50  
  Purchase #5 $80.85   7.502%   $86.9154   $86.92   $86.90   $86.90  
  Purchase #6 $201.79   5.507%   $212.9026   $212.90   $212.90   $212.90  
  Purchase #7 $238.64   6.520%   $254.1993   $254.20   $254.20   $254.20  
  7 purchase totals = $929.40       $985.3208   $985.32   $985.30   $985.30