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 $70.50   3.576%   $73.0211   $73.02   $73.00   $73.00  
  Purchase #2 $209.91   6.860%   $224.3098   $224.31   $224.30   $224.30  
  Purchase #3 $188.78   12.620%   $212.604   $212.60   $212.60   $212.60  
  Purchase #4 $112.76   4.644%   $117.9966   $118.00   $118.00   $118.00  
  Purchase #5 $154.77   4.634%   $161.942   $161.94   $161.95   $161.90  
  Purchase #6 $111.32   5.535%   $117.4816   $117.48   $117.50   $117.50  
  Purchase #7 $101.45   5.419%   $106.9476   $106.95   $106.95   $106.90  
  7 purchase totals = $949.49       $1,014.3027   $1,014.30   $1,014.30   $1,014.20