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 $117.65   7.542%   $126.5232   $126.52   $126.50   $126.50  
  Purchase #2 $170.35   7.607%   $183.3085   $183.31   $183.30   $183.30  
  Purchase #3 $196.87   7.798%   $212.2219   $212.22   $212.20   $212.20  
  Purchase #4 $26.75   3.441%   $27.6705   $27.67   $27.65   $27.70  
  Purchase #5 $37.31   9.336%   $40.7933   $40.79   $40.80   $40.80  
  Purchase #6 $200.88   9.582%   $220.1283   $220.13   $220.15   $220.10  
  Purchase #7 $142.38   7.509%   $153.0713   $153.07   $153.05   $153.10  
  7 purchase totals = $892.19       $963.7170   $963.71   $963.65   $963.70