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 $69.26   6.224%   $73.5707   $73.57   $73.55   $73.60  
  Purchase #2 $85.87   8.635%   $93.2849   $93.28   $93.30   $93.30  
  Purchase #3 $206.68   6.681%   $220.4883   $220.49   $220.50   $220.50  
  Purchase #4 $42.64   6.130%   $45.2538   $45.25   $45.25   $45.30  
  Purchase #5 $231.35   6.748%   $246.9615   $246.96   $246.95   $247.00  
  Purchase #6 $110.83   4.745%   $116.0889   $116.09   $116.10   $116.10  
  Purchase #7 $211.85   8.538%   $229.9378   $229.94   $229.95   $229.90  
  7 purchase totals = $958.48       $1,025.5859   $1,025.58   $1,025.60   $1,025.70