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 $28.41   13.812%   $32.334   $32.33   $32.35   $32.30  
  Purchase #2 $181.74   7.586%   $195.5268   $195.53   $195.55   $195.50  
  Purchase #3 $114.45   8.647%   $124.3465   $124.35   $124.35   $124.30  
  Purchase #4 $237.70   5.814%   $251.5199   $251.52   $251.50   $251.50  
  Purchase #5 $113.78   6.826%   $121.5466   $121.55   $121.55   $121.50  
  Purchase #6 $221.85   13.772%   $252.4032   $252.40   $252.40   $252.40  
  Purchase #7 $194.26   5.626%   $205.1891   $205.19   $205.20   $205.20  
  7 purchase totals = $1,092.19       $1,182.8661   $1,182.87   $1,182.90   $1,182.70