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 $117.60   7.402%   $126.3048   $126.30   $126.30   $126.30  
  Purchase #2 $205.38   13.341%   $232.7797   $232.78   $232.80   $232.80  
  Purchase #3 $53.99   8.498%   $58.5781   $58.58   $58.60   $58.60  
  Purchase #4 $198.52   13.208%   $224.7405   $224.74   $224.75   $224.70  
  Purchase #5 $127.75   11.509%   $142.4527   $142.45   $142.45   $142.50  
  Purchase #6 $92.91   3.467%   $96.1312   $96.13   $96.15   $96.10  
  Purchase #7 $249.46   12.766%   $281.3061   $281.31   $281.30   $281.30  
  7 purchase totals = $1,045.61       $1,162.2931   $1,162.29   $1,162.35   $1,162.30