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 $87.55   9.184%   $95.5906   $95.59   $95.60   $95.60  
  Purchase #2 $219.79   7.648%   $236.5995   $236.60   $236.60   $236.60  
  Purchase #3 $231.88   7.166%   $248.4965   $248.50   $248.50   $248.50  
  Purchase #4 $5.25   5.232%   $5.5247   $5.52   $5.50   $5.50  
  Purchase #5 $220.91   12.128%   $247.702   $247.70   $247.70   $247.70  
  Purchase #6 $204.79   5.596%   $216.25   $216.25   $216.25   $216.30  
  Purchase #7 $218.54   6.354%   $232.426   $232.43   $232.45   $232.40  
  7 purchase totals = $1,188.71       $1,282.5893   $1,282.59   $1,282.60   $1,282.60