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 $91.91   3.308%   $94.9504   $94.95   $94.95   $95.00  
  Purchase #2 $186.53   7.745%   $200.9767   $200.98   $201.00   $201.00  
  Purchase #3 $27.70   11.199%   $30.8021   $30.80   $30.80   $30.80  
  Purchase #4 $247.51   10.229%   $272.8278   $272.83   $272.85   $272.80  
  Purchase #5 $207.79   9.792%   $228.1368   $228.14   $228.15   $228.10  
  Purchase #6 $97.66   13.427%   $110.7728   $110.77   $110.75   $110.80  
  Purchase #7 $109.99   10.584%   $121.6313   $121.63   $121.65   $121.60  
  7 purchase totals = $969.09       $1,060.0979   $1,060.10   $1,060.15   $1,060.10