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 $77.69   12.849%   $87.6724   $87.67   $87.65   $87.70  
  Purchase #2 $208.71   11.542%   $232.7993   $232.80   $232.80   $232.80  
  Purchase #3 $53.44   8.550%   $58.0091   $58.01   $58.00   $58.00  
  Purchase #4 $177.58   11.313%   $197.6696   $197.67   $197.65   $197.70  
  Purchase #5 $197.39   6.132%   $209.494   $209.49   $209.50   $209.50  
  Purchase #6 $127.97   6.749%   $136.6067   $136.61   $136.60   $136.60  
  Purchase #7 $166.44   9.214%   $181.7758   $181.78   $181.80   $181.80  
  7 purchase totals = $1,009.22       $1,104.0269   $1,104.03   $1,104.00   $1,104.10