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 $62.99   5.572%   $66.4998   $66.50   $66.50   $66.50  
  Purchase #2 $191.70   13.129%   $216.8683   $216.87   $216.85   $216.90  
  Purchase #3 $92.73   3.674%   $96.1369   $96.14   $96.15   $96.10  
  Purchase #4 $62.64   5.453%   $66.0558   $66.06   $66.05   $66.10  
  Purchase #5 $190.25   5.330%   $200.3903   $200.39   $200.40   $200.40  
  Purchase #6 $188.27   12.280%   $211.3896   $211.39   $211.40   $211.40  
  Purchase #7 $188.39   9.173%   $205.671   $205.67   $205.65   $205.70  
  7 purchase totals = $976.97       $1,063.0117   $1,063.02   $1,063.00   $1,063.10