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 $61.36   5.273%   $64.5955   $64.60   $64.60   $64.60  
  Purchase #2 $217.42   12.826%   $245.3063   $245.31   $245.30   $245.30  
  Purchase #3 $190.84   6.200%   $202.6721   $202.67   $202.65   $202.70  
  Purchase #4 $79.28   3.795%   $82.2887   $82.29   $82.30   $82.30  
  Purchase #5 $83.31   4.696%   $87.2222   $87.22   $87.20   $87.20  
  Purchase #6 $193.52   12.240%   $217.2068   $217.21   $217.20   $217.20  
  Purchase #7 $243.66   8.621%   $264.6659   $264.67   $264.65   $264.70  
  7 purchase totals = $1,069.39       $1,163.9575   $1,163.97   $1,163.90   $1,164.00