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 $54.45   10.187%   $59.9968   $60.00   $60.00   $60.00  
  Purchase #2 $145.47   6.724%   $155.2514   $155.25   $155.25   $155.30  
  Purchase #3 $77.49   9.589%   $84.9205   $84.92   $84.90   $84.90  
  Purchase #4 $219.35   4.599%   $229.4379   $229.44   $229.45   $229.40  
  Purchase #5 $226.81   9.315%   $247.9374   $247.94   $247.95   $247.90  
  Purchase #6 $241.99   8.825%   $263.3456   $263.35   $263.35   $263.30  
  Purchase #7 $160.48   4.235%   $167.2763   $167.28   $167.30   $167.30  
  7 purchase totals = $1,126.04       $1,208.1659   $1,208.18   $1,208.20   $1,208.10