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 $241.70   8.474%   $262.1817   $262.18   $262.20   $262.20  
  Purchase #2 $172.91   7.658%   $186.1514   $186.15   $186.15   $186.20  
  Purchase #3 $203.37   12.295%   $228.3743   $228.37   $228.35   $228.40  
  Purchase #4 $83.49   12.642%   $94.0448   $94.04   $94.05   $94.00  
  Purchase #5 $110.44   11.364%   $122.9904   $122.99   $123.00   $123.00  
  Purchase #6 $89.45   12.170%   $100.3361   $100.34   $100.35   $100.30  
  Purchase #7 $151.84   11.281%   $168.9691   $168.97   $168.95   $169.00  
  7 purchase totals = $1,053.20       $1,163.0478   $1,163.04   $1,163.05   $1,163.10