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 $222.73   8.249%   $241.103   $241.10   $241.10   $241.10  
  Purchase #2 $147.38   12.325%   $165.5446   $165.54   $165.55   $165.50  
  Purchase #3 $59.36   6.704%   $63.3395   $63.34   $63.35   $63.30  
  Purchase #4 $191.29   11.792%   $213.8469   $213.85   $213.85   $213.80  
  Purchase #5 $53.44   5.484%   $56.3706   $56.37   $56.35   $56.40  
  Purchase #6 $166.35   13.481%   $188.7756   $188.78   $188.80   $188.80  
  Purchase #7 $190.48   3.759%   $197.6401   $197.64   $197.65   $197.60  
  7 purchase totals = $1,031.03       $1,126.6203   $1,126.62   $1,126.65   $1,126.50