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 $223.62   4.628%   $233.9691   $233.97   $233.95   $234.00  
  Purchase #2 $28.36   13.437%   $32.1707   $32.17   $32.15   $32.20  
  Purchase #3 $117.70   13.439%   $133.5177   $133.52   $133.50   $133.50  
  Purchase #4 $152.28   5.525%   $160.6935   $160.69   $160.70   $160.70  
  Purchase #5 $117.60   13.547%   $133.5313   $133.53   $133.55   $133.50  
  Purchase #6 $185.35   9.774%   $203.4661   $203.47   $203.45   $203.50  
  Purchase #7 $152.33   7.383%   $163.5765   $163.58   $163.60   $163.60  
  7 purchase totals = $977.24       $1,060.9249   $1,060.93   $1,060.90   $1,061.00