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 $222.63   7.477%   $239.276   $239.28   $239.30   $239.30  
  Purchase #2 $139.77   7.270%   $149.9313   $149.93   $149.95   $149.90  
  Purchase #3 $52.44   4.842%   $54.9791   $54.98   $55.00   $55.00  
  Purchase #4 $166.94   8.268%   $180.7426   $180.74   $180.75   $180.70  
  Purchase #5 $163.98   11.496%   $182.8311   $182.83   $182.85   $182.80  
  Purchase #6 $84.93   11.520%   $94.7139   $94.71   $94.70   $94.70  
  Purchase #7 $170.36   13.519%   $193.391   $193.39   $193.40   $193.40  
  7 purchase totals = $1,001.05       $1,095.8650   $1,095.86   $1,095.95   $1,095.80