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 $202.76   8.134%   $219.2525   $219.25   $219.25   $219.30  
  Purchase #2 $141.63   8.103%   $153.1063   $153.11   $153.10   $153.10  
  Purchase #3 $179.35   9.712%   $196.7685   $196.77   $196.75   $196.80  
  Purchase #4 $210.91   9.367%   $230.6659   $230.67   $230.65   $230.70  
  Purchase #5 $156.43   9.625%   $171.4864   $171.49   $171.50   $171.50  
  Purchase #6 $191.45   9.153%   $208.9734   $208.97   $208.95   $209.00  
  Purchase #7 $177.70   8.331%   $192.5042   $192.50   $192.50   $192.50  
  7 purchase totals = $1,260.23       $1,372.7572   $1,372.76   $1,372.70   $1,372.90