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 $117.86   7.385%   $126.564   $126.56   $126.55   $126.60  
  Purchase #2 $229.92   3.800%   $238.657   $238.66   $238.65   $238.70  
  Purchase #3 $51.52   11.424%   $57.4056   $57.41   $57.40   $57.40  
  Purchase #4 $239.35   7.507%   $257.318   $257.32   $257.30   $257.30  
  Purchase #5 $99.99   10.216%   $110.205   $110.21   $110.20   $110.20  
  Purchase #6 $212.79   11.173%   $236.565   $236.57   $236.55   $236.60  
  Purchase #7 $177.51   7.637%   $191.0664   $191.07   $191.05   $191.10  
  7 purchase totals = $1,128.94       $1,217.7810   $1,217.80   $1,217.70   $1,217.90