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 $217.41   7.466%   $233.6418   $233.64   $233.65   $233.60  
  Purchase #2 $247.55   3.275%   $255.6573   $255.66   $255.65   $255.70  
  Purchase #3 $105.52   11.577%   $117.7361   $117.74   $117.75   $117.70  
  Purchase #4 $199.42   6.599%   $212.5797   $212.58   $212.60   $212.60  
  Purchase #5 $162.56   3.539%   $168.313   $168.31   $168.30   $168.30  
  Purchase #6 $171.85   4.634%   $179.8135   $179.81   $179.80   $179.80  
  Purchase #7 $17.58   11.524%   $19.6059   $19.61   $19.60   $19.60  
  7 purchase totals = $1,121.89       $1,187.3473   $1,187.35   $1,187.35   $1,187.30