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 $171.59   13.235%   $194.2999   $194.30   $194.30   $194.30  
  Purchase #2 $228.91   3.623%   $237.2034   $237.20   $237.20   $237.20  
  Purchase #3 $37.83   11.614%   $42.2236   $42.22   $42.20   $42.20  
  Purchase #4 $99.59   6.630%   $106.1928   $106.19   $106.20   $106.20  
  Purchase #5 $168.81   4.131%   $175.7835   $175.78   $175.80   $175.80  
  Purchase #6 $226.96   6.406%   $241.4991   $241.50   $241.50   $241.50  
  Purchase #7 $11.94   10.123%   $13.1487   $13.15   $13.15   $13.10  
  7 purchase totals = $945.63       $1,010.3510   $1,010.34   $1,010.35   $1,010.30