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 $187.42   9.869%   $205.9165   $205.92   $205.90   $205.90  
  Purchase #2 $13.31   3.211%   $13.7374   $13.74   $13.75   $13.70  
  Purchase #3 $208.41   12.836%   $235.1615   $235.16   $235.15   $235.20  
  Purchase #4 $101.45   4.640%   $106.1573   $106.16   $106.15   $106.20  
  Purchase #5 $30.98   9.811%   $34.0194   $34.02   $34.00   $34.00  
  Purchase #6 $215.78   8.754%   $234.6694   $234.67   $234.65   $234.70  
  Purchase #7 $221.28   4.406%   $231.0296   $231.03   $231.05   $231.00  
  7 purchase totals = $978.63       $1,060.6911   $1,060.70   $1,060.65   $1,060.70