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 $214.33   13.638%   $243.5603   $243.56   $243.55   $243.60  
  Purchase #2 $187.31   11.527%   $208.9012   $208.90   $208.90   $208.90  
  Purchase #3 $31.39   3.594%   $32.5182   $32.52   $32.50   $32.50  
  Purchase #4 $51.76   13.121%   $58.5514   $58.55   $58.55   $58.60  
  Purchase #5 $142.75   10.678%   $157.9928   $157.99   $158.00   $158.00  
  Purchase #6 $227.74   11.492%   $253.9119   $253.91   $253.90   $253.90  
  Purchase #7 $207.95   5.614%   $219.6243   $219.62   $219.60   $219.60  
  7 purchase totals = $1,063.23       $1,175.0601   $1,175.05   $1,175.00   $1,175.10