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 $54.55   13.184%   $61.7419   $61.74   $61.75   $61.70  
  Purchase #2 $54.86   5.367%   $57.8043   $57.80   $57.80   $57.80  
  Purchase #3 $244.92   5.218%   $257.6999   $257.70   $257.70   $257.70  
  Purchase #4 $212.35   8.328%   $230.0345   $230.03   $230.05   $230.00  
  Purchase #5 $224.86   8.804%   $244.6567   $244.66   $244.65   $244.70  
  Purchase #6 $177.96   4.482%   $185.9362   $185.94   $185.95   $185.90  
  Purchase #7 $146.67   6.715%   $156.5189   $156.52   $156.50   $156.50  
  7 purchase totals = $1,116.17       $1,194.3924   $1,194.39   $1,194.40   $1,194.30