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 $61.74   10.217%   $68.048   $68.05   $68.05   $68.00  
  Purchase #2 $199.91   6.654%   $213.212   $213.21   $213.20   $213.20  
  Purchase #3 $37.70   7.282%   $40.4453   $40.45   $40.45   $40.40  
  Purchase #4 $103.26   4.620%   $108.0306   $108.03   $108.05   $108.00  
  Purchase #5 $63.26   4.614%   $66.1788   $66.18   $66.20   $66.20  
  Purchase #6 $164.29   10.611%   $181.7228   $181.72   $181.70   $181.70  
  Purchase #7 $96.49   3.583%   $99.9472   $99.95   $99.95   $99.90  
  7 purchase totals = $726.65       $777.5847   $777.59   $777.60   $777.40