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 $90.87   4.816%   $95.2463   $95.25   $95.25   $95.20  
  Purchase #2 $234.54   7.573%   $252.3017   $252.30   $252.30   $252.30  
  Purchase #3 $38.82   11.617%   $43.3297   $43.33   $43.35   $43.30  
  Purchase #4 $124.56   7.258%   $133.6006   $133.60   $133.60   $133.60  
  Purchase #5 $143.82   8.440%   $155.9584   $155.96   $155.95   $156.00  
  Purchase #6 $68.35   9.529%   $74.8631   $74.86   $74.85   $74.90  
  Purchase #7 $23.70   11.616%   $26.453   $26.45   $26.45   $26.50  
  7 purchase totals = $724.66       $781.7528   $781.75   $781.75   $781.80