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 $194.84   11.674%   $217.5856   $217.59   $217.60   $217.60  
  Purchase #2 $226.36   8.779%   $246.2321   $246.23   $246.25   $246.20  
  Purchase #3 $66.83   5.268%   $70.3506   $70.35   $70.35   $70.40  
  Purchase #4 $11.51   6.562%   $12.2653   $12.27   $12.25   $12.30  
  Purchase #5 $169.35   12.746%   $190.9354   $190.94   $190.95   $190.90  
  Purchase #6 $194.86   10.718%   $215.7451   $215.75   $215.75   $215.70  
  Purchase #7 $235.52   5.657%   $248.8434   $248.84   $248.85   $248.80  
  7 purchase totals = $1,099.27       $1,201.9575   $1,201.97   $1,202.00   $1,201.90