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 $86.98   10.793%   $96.3678   $96.37   $96.35   $96.40  
  Purchase #2 $82.99   8.693%   $90.2043   $90.20   $90.20   $90.20  
  Purchase #3 $159.70   7.540%   $171.7414   $171.74   $171.75   $171.70  
  Purchase #4 $29.35   7.743%   $31.6226   $31.62   $31.60   $31.60  
  Purchase #5 $128.62   13.854%   $146.439   $146.44   $146.45   $146.40  
  Purchase #6 $194.48   5.724%   $205.612   $205.61   $205.60   $205.60  
  Purchase #7 $202.49   8.281%   $219.2582   $219.26   $219.25   $219.30  
  7 purchase totals = $884.61       $961.2453   $961.24   $961.20   $961.20