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 $186.84   4.235%   $194.7527   $194.75   $194.75   $194.80  
  Purchase #2 $41.54   11.495%   $46.315   $46.32   $46.30   $46.30  
  Purchase #3 $226.76   3.170%   $233.9483   $233.95   $233.95   $233.90  
  Purchase #4 $244.90   5.216%   $257.674   $257.67   $257.65   $257.70  
  Purchase #5 $34.79   10.786%   $38.5424   $38.54   $38.55   $38.50  
  Purchase #6 $192.56   11.218%   $214.1614   $214.16   $214.15   $214.20  
  Purchase #7 $57.94   5.245%   $60.979   $60.98   $61.00   $61.00  
  7 purchase totals = $985.33       $1,046.3728   $1,046.37   $1,046.35   $1,046.40