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 $209.81   12.358%   $235.7383   $235.74   $235.75   $235.70  
  Purchase #2 $219.57   5.173%   $230.9284   $230.93   $230.95   $230.90  
  Purchase #3 $109.27   12.184%   $122.5835   $122.58   $122.60   $122.60  
  Purchase #4 $157.83   6.125%   $167.4971   $167.50   $167.50   $167.50  
  Purchase #5 $152.60   12.262%   $171.3118   $171.31   $171.30   $171.30  
  Purchase #6 $191.52   11.685%   $213.8991   $213.90   $213.90   $213.90  
  Purchase #7 $200.94   8.723%   $218.468   $218.47   $218.45   $218.50  
  7 purchase totals = $1,241.54       $1,360.4262   $1,360.43   $1,360.45   $1,360.40