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 $64.55   6.870%   $68.9846   $68.98   $69.00   $69.00  
  Purchase #2 $217.88   3.280%   $225.0265   $225.03   $225.05   $225.00  
  Purchase #3 $149.62   6.775%   $159.7568   $159.76   $159.75   $159.80  
  Purchase #4 $68.88   3.851%   $71.5326   $71.53   $71.55   $71.50  
  Purchase #5 $74.81   10.363%   $82.5626   $82.56   $82.55   $82.60  
  Purchase #6 $232.73   9.818%   $255.5794   $255.58   $255.60   $255.60  
  Purchase #7 $222.64   9.358%   $243.4747   $243.47   $243.45   $243.50  
  7 purchase totals = $1,031.11       $1,106.9172   $1,106.91   $1,106.95   $1,107.00