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 $85.76   11.744%   $95.8317   $95.83   $95.85   $95.80  
  Purchase #2 $224.47   8.861%   $244.3603   $244.36   $244.35   $244.40  
  Purchase #3 $130.82   5.482%   $137.9916   $137.99   $138.00   $138.00  
  Purchase #4 $55.99   11.523%   $62.4417   $62.44   $62.45   $62.40  
  Purchase #5 $228.44   8.408%   $247.6472   $247.65   $247.65   $247.60  
  Purchase #6 $19.97   7.230%   $21.4138   $21.41   $21.40   $21.40  
  Purchase #7 $228.91   6.466%   $243.7113   $243.71   $243.70   $243.70  
  7 purchase totals = $974.36       $1,053.3976   $1,053.39   $1,053.40   $1,053.30