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 $62.78   9.126%   $68.5093   $68.51   $68.50   $68.50  
  Purchase #2 $205.31   9.689%   $225.2025   $225.20   $225.20   $225.20  
  Purchase #3 $114.47   8.319%   $123.9928   $123.99   $124.00   $124.00  
  Purchase #4 $102.87   5.787%   $108.8231   $108.82   $108.80   $108.80  
  Purchase #5 $65.64   4.577%   $68.6443   $68.64   $68.65   $68.60  
  Purchase #6 $220.77   6.119%   $234.2789   $234.28   $234.30   $234.30  
  Purchase #7 $175.68   6.244%   $186.6495   $186.65   $186.65   $186.60  
  7 purchase totals = $947.52       $1,016.1004   $1,016.09   $1,016.10   $1,016.00