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 $209.94   3.645%   $217.5923   $217.59   $217.60   $217.60  
  Purchase #2 $215.95   13.461%   $245.019   $245.02   $245.00   $245.00  
  Purchase #3 $95.96   13.195%   $108.6219   $108.62   $108.60   $108.60  
  Purchase #4 $64.52   7.469%   $69.339   $69.34   $69.35   $69.30  
  Purchase #5 $192.37   5.386%   $202.731   $202.73   $202.75   $202.70  
  Purchase #6 $90.53   3.535%   $93.7302   $93.73   $93.75   $93.70  
  Purchase #7 $85.91   12.418%   $96.5783   $96.58   $96.60   $96.60  
  7 purchase totals = $955.18       $1,033.6117   $1,033.61   $1,033.65   $1,033.50