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 $72.69   4.822%   $76.1951   $76.20   $76.20   $76.20  
  Purchase #2 $113.62   11.148%   $126.2864   $126.29   $126.30   $126.30  
  Purchase #3 $182.76   5.305%   $192.4554   $192.46   $192.45   $192.50  
  Purchase #4 $200.47   6.218%   $212.9352   $212.94   $212.95   $212.90  
  Purchase #5 $119.85   9.815%   $131.6133   $131.61   $131.60   $131.60  
  Purchase #6 $205.52   9.659%   $225.3712   $225.37   $225.35   $225.40  
  Purchase #7 $109.70   9.583%   $120.2126   $120.21   $120.20   $120.20  
  7 purchase totals = $1,004.61       $1,085.0692   $1,085.08   $1,085.05   $1,085.10