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 $86.89   8.276%   $94.081   $94.08   $94.10   $94.10  
  Purchase #2 $214.37   6.777%   $228.8979   $228.90   $228.90   $228.90  
  Purchase #3 $142.38   4.381%   $148.6177   $148.62   $148.60   $148.60  
  Purchase #4 $230.94   5.107%   $242.7341   $242.73   $242.75   $242.70  
  Purchase #5 $25.40   4.763%   $26.6098   $26.61   $26.60   $26.60  
  Purchase #6 $48.69   3.243%   $50.269   $50.27   $50.25   $50.30  
  Purchase #7 $158.50   7.364%   $170.1719   $170.17   $170.15   $170.20  
  7 purchase totals = $907.17       $961.3814   $961.38   $961.35   $961.40