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 $162.45   7.247%   $174.2228   $174.22   $174.20   $174.20  
  Purchase #2 $140.54   10.794%   $155.7099   $155.71   $155.70   $155.70  
  Purchase #3 $68.60   8.309%   $74.3   $74.30   $74.30   $74.30  
  Purchase #4 $209.86   10.430%   $231.7484   $231.75   $231.75   $231.70  
  Purchase #5 $207.45   5.501%   $218.8618   $218.86   $218.85   $218.90  
  Purchase #6 $61.79   4.748%   $64.7238   $64.72   $64.70   $64.70  
  Purchase #7 $175.62   8.737%   $190.9639   $190.96   $190.95   $191.00  
  7 purchase totals = $1,026.31       $1,110.5306   $1,110.52   $1,110.45   $1,110.50