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 $117.41   7.296%   $125.9762   $125.98   $126.00   $126.00  
  Purchase #2 $7.74   3.278%   $7.9937   $7.99   $8.00   $8.00  
  Purchase #3 $39.87   8.793%   $43.3758   $43.38   $43.40   $43.40  
  Purchase #4 $85.98   8.600%   $93.3743   $93.37   $93.35   $93.40  
  Purchase #5 $22.82   8.375%   $24.7312   $24.73   $24.75   $24.70  
  Purchase #6 $68.83   7.322%   $73.8697   $73.87   $73.85   $73.90  
  Purchase #7 $41.86   6.398%   $44.5382   $44.54   $44.55   $44.50  
  7 purchase totals = $384.51       $413.8591   $413.86   $413.90   $413.90