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 $197.94   7.411%   $212.6093   $212.61   $212.60   $212.60  
  Purchase #2 $164.44   12.649%   $185.24   $185.24   $185.25   $185.20  
  Purchase #3 $65.39   13.322%   $74.1013   $74.10   $74.10   $74.10  
  Purchase #4 $121.48   7.574%   $130.6809   $130.68   $130.70   $130.70  
  Purchase #5 $244.93   10.118%   $269.712   $269.71   $269.70   $269.70  
  Purchase #6 $26.70   4.779%   $27.976   $27.98   $28.00   $28.00  
  Purchase #7 $97.58   3.386%   $100.8841   $100.88   $100.90   $100.90  
  7 purchase totals = $918.46       $1,001.2036   $1,001.20   $1,001.25   $1,001.20