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 $35.70   6.532%   $38.0319   $38.03   $38.05   $38.00  
  Purchase #2 $172.62   13.633%   $196.1533   $196.15   $196.15   $196.20  
  Purchase #3 $41.91   12.203%   $47.0243   $47.02   $47.00   $47.00  
  Purchase #4 $111.28   6.813%   $118.8615   $118.86   $118.85   $118.90  
  Purchase #5 $211.67   11.791%   $236.628   $236.63   $236.65   $236.60  
  Purchase #6 $107.94   4.245%   $112.5221   $112.52   $112.50   $112.50  
  Purchase #7 $205.88   6.254%   $218.7557   $218.76   $218.75   $218.80  
  7 purchase totals = $887.00       $967.9768   $967.97   $967.95   $968.00