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 $182.84   10.703%   $202.4094   $202.41   $202.40   $202.40  
  Purchase #2 $193.94   6.114%   $205.7975   $205.80   $205.80   $205.80  
  Purchase #3 $11.65   7.711%   $12.5483   $12.55   $12.55   $12.50  
  Purchase #4 $126.63   12.127%   $141.9864   $141.99   $142.00   $142.00  
  Purchase #5 $164.56   11.499%   $183.4828   $183.48   $183.50   $183.50  
  Purchase #6 $108.58   3.467%   $112.3445   $112.34   $112.35   $112.30  
  Purchase #7 $150.42   3.214%   $155.2545   $155.25   $155.25   $155.30  
  7 purchase totals = $938.62       $1,013.8234   $1,013.82   $1,013.85   $1,013.80