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 $41.94   8.869%   $45.6597   $45.66   $45.65   $45.70  
  Purchase #2 $61.44   12.617%   $69.1919   $69.19   $69.20   $69.20  
  Purchase #3 $187.65   8.301%   $203.2268   $203.23   $203.25   $203.20  
  Purchase #4 $185.54   11.848%   $207.5228   $207.52   $207.50   $207.50  
  Purchase #5 $110.40   9.683%   $121.09   $121.09   $121.10   $121.10  
  Purchase #6 $201.67   8.202%   $218.211   $218.21   $218.20   $218.20  
  Purchase #7 $147.59   3.216%   $152.3365   $152.34   $152.35   $152.30  
  7 purchase totals = $936.23       $1,017.2387   $1,017.24   $1,017.25   $1,017.20