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 $175.96   10.817%   $194.9936   $194.99   $195.00   $195.00  
  Purchase #2 $60.97   8.775%   $66.3201   $66.32   $66.30   $66.30  
  Purchase #3 $234.32   11.265%   $260.7161   $260.72   $260.70   $260.70  
  Purchase #4 $41.92   9.381%   $45.8525   $45.85   $45.85   $45.90  
  Purchase #5 $219.54   7.287%   $235.5379   $235.54   $235.55   $235.50  
  Purchase #6 $73.81   3.844%   $76.6473   $76.65   $76.65   $76.60  
  Purchase #7 $145.73   11.582%   $162.6084   $162.61   $162.60   $162.60  
  7 purchase totals = $952.25       $1,042.6759   $1,042.68   $1,042.65   $1,042.60