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 $213.91   7.842%   $230.6848   $230.68   $230.70   $230.70  
  Purchase #2 $56.64   3.380%   $58.5544   $58.55   $58.55   $58.60  
  Purchase #3 $49.94   12.714%   $56.2894   $56.29   $56.30   $56.30  
  Purchase #4 $214.41   6.839%   $229.0735   $229.07   $229.05   $229.10  
  Purchase #5 $243.46   11.773%   $272.1225   $272.12   $272.10   $272.10  
  Purchase #6 $173.90   7.247%   $186.5025   $186.50   $186.50   $186.50  
  Purchase #7 $32.94   7.182%   $35.3058   $35.31   $35.30   $35.30  
  7 purchase totals = $985.20       $1,068.5329   $1,068.52   $1,068.50   $1,068.60