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 $63.41   13.174%   $71.7636   $71.76   $71.75   $71.80  
  Purchase #2 $41.57   12.348%   $46.7031   $46.70   $46.70   $46.70  
  Purchase #3 $209.51   12.201%   $235.0723   $235.07   $235.05   $235.10  
  Purchase #4 $185.38   11.826%   $207.303   $207.30   $207.30   $207.30  
  Purchase #5 $121.63   5.365%   $128.1554   $128.16   $128.15   $128.20  
  Purchase #6 $185.57   4.850%   $194.5701   $194.57   $194.55   $194.60  
  Purchase #7 $154.90   7.366%   $166.3099   $166.31   $166.30   $166.30  
  7 purchase totals = $961.97       $1,049.8774   $1,049.87   $1,049.80   $1,050.00